library: libTree #include "TTree.h" |
TTree
class description - header file - source file
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Function Members (Methods)
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public:
| TTree() |
| TTree(const char* name, const char* title, Int_t splitlevel = 99) |
virtual | ~TTree() |
void | TObject::AbstractMethod(const char* method) const |
virtual TFriendElement* | AddFriend(const char* treename, const char* filename = "") |
virtual TFriendElement* | AddFriend(const char* treename, TFile* file) |
virtual TFriendElement* | AddFriend(TTree* tree, const char* alias = "", Bool_t warn = kFALSE) |
virtual void | AddTotBytes(Int_t tot) |
virtual void | AddZipBytes(Int_t zip) |
virtual void | TObject::AppendPad(Option_t* option = "") |
virtual Long64_t | AutoSave(Option_t* option = "") |
virtual Int_t | Branch(TList* list, Int_t bufsize = 32000, Int_t splitlevel = 99) |
virtual Int_t | Branch(const char* folder, Int_t bufsize = 32000, Int_t splitlevel = 99) |
virtual Int_t | Branch(TCollection* list, Int_t bufsize = 32000, Int_t splitlevel = 99, const char* name = "") |
virtual TBranch* | Branch(const char* name, void* address, const char* leaflist, Int_t bufsize = 32000) |
TBranch* | Branch(const char* name, void*** addobj, Int_t bufsize = 32000, Int_t splitlevel = 99) |
TBranch* | Branch(const char* name, const char* classname, void*** addobj, Int_t bufsize = 32000, Int_t splitlevel = 99) |
virtual TBranch* | BranchOld(const char* name, const char* classname, void* addobj, Int_t bufsize = 32000, Int_t splitlevel = 1) |
virtual TBranch* | BranchRef() |
virtual TBranch* | Bronch(const char* name, const char* classname, void* addobj, Int_t bufsize = 32000, Int_t splitlevel = 99) |
virtual void | Browse(TBrowser*) |
virtual Int_t | BuildIndex(const char* majorname, const char* minorname = "0") |
TStreamerInfo* | BuildStreamerInfo(TClass* cl, void* pointer = 0) |
static TClass* | Class() |
virtual const char* | TObject::ClassName() const |
virtual void | TNamed::Clear(Option_t* option = "") |
virtual TObject* | TNamed::Clone(const char* newname = "") const |
virtual TTree* | CloneTree(Long64_t nentries = -1, Option_t* option = "") |
virtual Int_t | TNamed::Compare(const TObject* obj) const |
virtual void | TNamed::Copy(TObject& named) const |
virtual void | CopyAddresses(TTree*) |
virtual Long64_t | CopyEntries(TTree* tree, Long64_t nentries = -1) |
virtual TTree* | CopyTree(const char* selection, Option_t* option = "", Long64_t nentries = 1000000000, Long64_t firstentry = 0) |
virtual TBasket* | CreateBasket(TBranch*) |
Int_t | Debug() const |
virtual void | Delete(Option_t* option = "") |
Int_t | TAttLine::DistancetoLine(Int_t px, Int_t py, Double_t xp1, Double_t yp1, Double_t xp2, Double_t yp2) |
virtual Int_t | TObject::DistancetoPrimitive(Int_t px, Int_t py) |
virtual void | Draw(Option_t* opt) |
virtual Long64_t | Draw(const char* varexp, const TCut& selection, Option_t* option = "", Long64_t nentries = 1000000000, Long64_t firstentry = 0) |
virtual Long64_t | Draw(const char* varexp, const char* selection, Option_t* option = "", Long64_t nentries = 1000000000, Long64_t firstentry = 0) |
virtual void | TObject::DrawClass() const |
virtual TObject* | TObject::DrawClone(Option_t* option = "") const |
virtual void | DropBaskets() |
virtual void | DropBuffers(Int_t nbytes) |
virtual void | TObject::Dump() const |
virtual void | TObject::Error(const char* method, const char* msgfmt) const |
virtual void | TObject::Execute(const char* method, const char* params, Int_t* error = 0) |
virtual void | TObject::Execute(TMethod* method, TObjArray* params, Int_t* error = 0) |
virtual void | TObject::ExecuteEvent(Int_t event, Int_t px, Int_t py) |
virtual void | TObject::Fatal(const char* method, const char* msgfmt) const |
virtual Int_t | Fill() |
virtual void | TNamed::FillBuffer(char*& buffer) |
virtual TBranch* | FindBranch(const char* name) |
virtual TLeaf* | FindLeaf(const char* name) |
virtual TObject* | TObject::FindObject(const char* name) const |
virtual TObject* | TObject::FindObject(const TObject* obj) const |
virtual Long64_t | Fit(const char* funcname, const char* varexp, const char* selection = "", Option_t* option = "", Option_t* goption = "", Long64_t nentries = 1000000000, Long64_t firstentry = 0) |
virtual const char* | GetAlias(const char* aliasName) const |
virtual TBranch* | GetBranch(const char* name) |
virtual TBranchRef* | GetBranchRef() const |
virtual Bool_t | GetBranchStatus(const char* branchname) const |
static Int_t | GetBranchStyle() |
virtual Long64_t | GetCacheSize() const |
virtual Long64_t | GetChainEntryNumber(Long64_t entry) const |
virtual Long64_t | GetChainOffset() const |
TFile* | GetCurrentFile() const |
Long64_t | GetDebugMax() const |
Long64_t | GetDebugMin() const |
TDirectory* | GetDirectory() const |
virtual Option_t* | TObject::GetDrawOption() const |
static Long_t | TObject::GetDtorOnly() |
virtual Long64_t | GetEntries() const |
virtual Long64_t | GetEntries(const char* selection) |
virtual Long64_t | GetEntriesFast() const |
virtual Long64_t | GetEntriesFriend() const |
virtual Int_t | GetEntry(Long64_t entry = 0, Int_t getall = 0) |
virtual Long64_t | GetEntryNumber(Long64_t entry) const |
virtual Long64_t | GetEntryNumberWithBestIndex(Int_t major, Int_t minor = 0) const |
virtual Long64_t | GetEntryNumberWithIndex(Int_t major, Int_t minor = 0) const |
virtual Int_t | GetEntryWithIndex(Int_t major, Int_t minor = 0) |
virtual Long64_t | GetEstimate() const |
Int_t | GetEvent(Long64_t entry = 0, Int_t getall = 0) |
TEventList* | GetEventList() const |
virtual Int_t | GetFileNumber() const |
virtual Color_t | TAttFill::GetFillColor() const |
virtual Style_t | TAttFill::GetFillStyle() const |
virtual const char* | GetFriendAlias(TTree*) const |
TH1* | GetHistogram() |
virtual const char* | TObject::GetIconName() const |
virtual Int_t* | GetIndex() |
virtual Double_t* | GetIndexValues() |
virtual TIterator* | GetIteratorOnAllLeaves(Bool_t dir = kIterForward) |
virtual TLeaf* | GetLeaf(const char* name) |
virtual Color_t | TAttLine::GetLineColor() const |
virtual Style_t | TAttLine::GetLineStyle() const |
virtual Width_t | TAttLine::GetLineWidth() const |
virtual TSeqCollection* | GetListOfAliases() const |
virtual TObjArray* | GetListOfBranches() |
virtual TList* | GetListOfClones() |
virtual TList* | GetListOfFriends() const |
virtual TObjArray* | GetListOfLeaves() |
Int_t | GetMakeClass() const |
virtual Color_t | TAttMarker::GetMarkerColor() const |
virtual Size_t | TAttMarker::GetMarkerSize() const |
virtual Style_t | TAttMarker::GetMarkerStyle() const |
virtual Long64_t | GetMaxEntryLoop() const |
virtual Double_t | GetMaximum(const char* columname) |
static Long64_t | GetMaxTreeSize() |
virtual Long64_t | GetMaxVirtualSize() const |
virtual Double_t | GetMinimum(const char* columname) |
virtual const char* | TNamed::GetName() const |
virtual Int_t | GetNbranches() |
TObject* | GetNotify() const |
virtual char* | TObject::GetObjectInfo(Int_t px, Int_t py) const |
static Bool_t | TObject::GetObjectStat() |
virtual Option_t* | TObject::GetOption() const |
virtual Int_t | GetPacketSize() const |
TVirtualTreePlayer* | GetPlayer() |
virtual Long64_t | GetReadEntry() const |
virtual Long64_t | GetReadEvent() const |
virtual Int_t | GetScanField() const |
TTreeFormula* | GetSelect() |
virtual Long64_t | GetSelectedRows() |
virtual Int_t | GetTimerInterval() const |
virtual const char* | TNamed::GetTitle() const |
virtual Long64_t | GetTotBytes() const |
virtual TTree* | GetTree() const |
virtual TVirtualIndex* | GetTreeIndex() const |
virtual Int_t | GetTreeNumber() const |
virtual UInt_t | TObject::GetUniqueID() const |
virtual Int_t | GetUpdate() const |
virtual TList* | GetUserInfo() |
virtual Double_t* | GetV1() |
virtual Double_t* | GetV2() |
virtual Double_t* | GetV3() |
virtual Double_t* | GetV4() |
TTreeFormula* | GetVar1() |
TTreeFormula* | GetVar2() |
TTreeFormula* | GetVar3() |
TTreeFormula* | GetVar4() |
virtual Double_t* | GetW() |
virtual Double_t | GetWeight() const |
virtual Long64_t | GetZipBytes() const |
virtual Bool_t | TObject::HandleTimer(TTimer* timer) |
virtual ULong_t | TNamed::Hash() const |
virtual void | IncrementTotalBuffers(Int_t nbytes) |
virtual void | TObject::Info(const char* method, const char* msgfmt) const |
virtual Bool_t | TObject::InheritsFrom(const char* classname) const |
virtual Bool_t | TObject::InheritsFrom(const TClass* cl) const |
virtual void | TObject::Inspect() const |
void | TObject::InvertBit(UInt_t f) |
virtual TClass* | IsA() const |
virtual Bool_t | TObject::IsEqual(const TObject* obj) const |
virtual Bool_t | IsFolder() const |
Bool_t | TObject::IsOnHeap() const |
virtual Bool_t | TNamed::IsSortable() const |
virtual Bool_t | TAttFill::IsTransparent() const |
Bool_t | TObject::IsZombie() const |
virtual Int_t | LoadBaskets(Long64_t maxmemory = 2000000000) |
virtual Long64_t | LoadTree(Long64_t entry) |
virtual Long64_t | LoadTreeFriend(Long64_t entry, TTree* T) |
virtual void | TNamed::ls(Option_t* option = "") const |
virtual Int_t | MakeClass(const char* classname = "0", Option_t* option = "") |
virtual Int_t | MakeCode(const char* filename = "0") |
virtual Int_t | MakeProxy(const char* classname, const char* macrofilename = "0", const char* cutfilename = "0", const char* option = "0", Int_t maxUnrolling = 3) |
virtual Int_t | MakeSelector(const char* selector = "0") |
void | TObject::MayNotUse(const char* method) const |
Bool_t | MemoryFull(Int_t nbytes) |
virtual Long64_t | Merge(TCollection* list, Option_t* option = "") |
static TTree* | MergeTrees(TList* list, Option_t* option = "") |
virtual void | TAttLine::Modify() |
virtual Bool_t | Notify() |
static void | TObject::operator delete(void* ptr) |
static void | TObject::operator delete(void* ptr, void* vp) |
static void | TObject::operator delete[](void* ptr) |
static void | TObject::operator delete[](void* ptr, void* vp) |
void* | TObject::operator new(size_t sz) |
void* | TObject::operator new(size_t sz, void* vp) |
void* | TObject::operator new[](size_t sz) |
void* | TObject::operator new[](size_t sz, void* vp) |
virtual void | TObject::Paint(Option_t* option = "") |
virtual void | TObject::Pop() |
TPrincipal* | Principal(const char* varexp = "", const char* selection = "", Option_t* option = "np", Long64_t nentries = 1000000000, Long64_t firstentry = 0) |
virtual void | Print(Option_t* option = "") const |
virtual Long64_t | Process(const char* filename, Option_t* option = "", Long64_t nentries = 1000000000, Long64_t firstentry = 0) |
virtual Long64_t | Process(TSelector* selector, Option_t* option = "", Long64_t nentries = 1000000000, Long64_t firstentry = 0) |
virtual Long64_t | Project(const char* hname, const char* varexp, const char* selection = "", Option_t* option = "", Long64_t nentries = 1000000000, Long64_t firstentry = 0) |
virtual TSQLResult* | Query(const char* varexp = "", const char* selection = "", Option_t* option = "", Long64_t nentries = 1000000000, Long64_t firstentry = 0) |
virtual Int_t | TObject::Read(const char* name) |
virtual Long64_t | ReadFile(const char* filename, const char* branchDescriptor = "") |
virtual void | TObject::RecursiveRemove(TObject* obj) |
virtual void | Refresh() |
virtual void | RemoveFriend(TTree*) |
virtual void | Reset(Option_t* option = "") |
virtual void | TAttFill::ResetAttFill(Option_t* option = "") |
virtual void | TAttLine::ResetAttLine(Option_t* option = "") |
virtual void | TAttMarker::ResetAttMarker(Option_t* toption = "") |
void | TObject::ResetBit(UInt_t f) |
virtual void | ResetBranchAddresses() |
virtual void | TObject::SaveAs(const char* filename = "", Option_t* option = "") const |
virtual void | TAttFill::SaveFillAttributes(ostream& out, const char* name, Int_t coldef = 1, Int_t stydef = 1001) |
virtual void | TAttLine::SaveLineAttributes(ostream& out, const char* name, Int_t coldef = 1, Int_t stydef = 1, Int_t widdef = 1) |
virtual void | TAttMarker::SaveMarkerAttributes(ostream& out, const char* name, Int_t coldef = 1, Int_t stydef = 1, Int_t sizdef = 1) |
virtual void | TObject::SavePrimitive(ostream& out, Option_t* option = "") |
virtual Long64_t | Scan(const char* varexp = "", const char* selection = "", Option_t* option = "", Long64_t nentries = 1000000000, Long64_t firstentry = 0) |
virtual Bool_t | SetAlias(const char* aliasName, const char* aliasFormula) |
virtual void | SetAutoSave(Long64_t autos = 10000000) |
virtual void | SetBasketSize(const char* bname, Int_t buffsize = 16000) |
void | TObject::SetBit(UInt_t f) |
void | TObject::SetBit(UInt_t f, Bool_t set) |
void | SetBranchAddress(const char* bname, void** add, TBranch** ptr = 0) |
virtual void | SetBranchAddress(const char* bname, void* add, TClass* realClass, EDataType datatype, Bool_t isptr) |
virtual void | SetBranchAddress(const char* bname, void* add, TBranch** ptr, TClass* realClass, EDataType datatype, Bool_t isptr) |
virtual void | SetBranchStatus(const char* bname, Bool_t status = 1, UInt_t* found = 0) |
static void | SetBranchStyle(Int_t style = 1) |
virtual void | SetCacheSize(Long64_t cachesize = 10000000) |
virtual void | SetChainOffset(Long64_t offset = 0) |
virtual void | SetCircular(Long64_t maxEntries) |
virtual void | SetDebug(Int_t level = 1, Long64_t min = 0, Long64_t max = 9999999) |
virtual void | SetDirectory(TDirectory* dir) |
virtual void | TObject::SetDrawOption(Option_t* option = "") |
static void | TObject::SetDtorOnly(void* obj) |
virtual Long64_t | SetEntries(Long64_t n = -1) |
virtual void | SetEstimate(Long64_t nentries = 10000) |
virtual void | SetEventList(TEventList* list) |
virtual void | SetFileNumber(Int_t number = 0) |
virtual void | TAttFill::SetFillAttributes() |
virtual void | TAttFill::SetFillColor(Color_t fcolor) |
virtual void | TAttFill::SetFillStyle(Style_t fstyle) |
virtual void | TAttLine::SetLineAttributes() |
virtual void | TAttLine::SetLineColor(Color_t lcolor) |
virtual void | TAttLine::SetLineStyle(Style_t lstyle) |
virtual void | TAttLine::SetLineWidth(Width_t lwidth) |
virtual void | SetMakeClass(Int_t make) |
virtual void | TAttMarker::SetMarkerAttributes() |
virtual void | TAttMarker::SetMarkerColor(Color_t tcolor = 1) |
virtual void | TAttMarker::SetMarkerSize(Size_t msize = 1) |
virtual void | TAttMarker::SetMarkerStyle(Style_t mstyle = 1) |
virtual void | SetMaxEntryLoop(Long64_t maxev = 1000000000) |
static void | SetMaxTreeSize(Long64_t maxsize = 1900000000) |
virtual void | SetMaxVirtualSize(Long64_t size = 0) |
virtual void | SetName(const char* name) |
virtual void | TNamed::SetNameTitle(const char* name, const char* title) |
virtual void | SetNotify(TObject* obj) |
virtual void | SetObject(const char* name, const char* title) |
static void | TObject::SetObjectStat(Bool_t stat) |
virtual void | SetScanField(Int_t n = 50) |
virtual void | SetTimerInterval(Int_t msec = 333) |
virtual void | TNamed::SetTitle(const char* title = "") |
virtual void | SetTreeIndex(TVirtualIndex* index) |
virtual void | TObject::SetUniqueID(UInt_t uid) |
virtual void | SetUpdate(Int_t freq = 0) |
virtual void | SetWeight(Double_t w = 1, Option_t* option = "") |
virtual void | Show(Long64_t entry = -1, Int_t lenmax = 20) |
virtual void | ShowMembers(TMemberInspector& insp, char* parent) |
virtual Int_t | TNamed::Sizeof() const |
virtual void | StartViewer() |
virtual void | Streamer(TBuffer& b) |
void | StreamerNVirtual(TBuffer& b) |
virtual void | TObject::SysError(const char* method, const char* msgfmt) const |
Bool_t | TObject::TestBit(UInt_t f) const |
Int_t | TObject::TestBits(UInt_t f) const |
virtual Long64_t | UnbinnedFit(const char* funcname, const char* varexp, const char* selection = "", Option_t* option = "", Long64_t nentries = 1000000000, Long64_t firstentry = 0) |
virtual void | UseCurrentStyle() |
virtual void | TObject::Warning(const char* method, const char* msgfmt) const |
virtual Int_t | TObject::Write(const char* name = "0", Int_t option = 0, Int_t bufsize = 0) |
virtual Int_t | TObject::Write(const char* name = "0", Int_t option = 0, Int_t bufsize = 0) const |
protected:
void | AddClone(TTree*) |
virtual TBranch* | BranchImp(const char* branchname, TClass* ptrClass, void* addobj, Int_t bufsize, Int_t splitlevel) |
virtual TBranch* | BranchImp(const char* branchname, const char* classname, TClass* ptrClass, void* addobj, Int_t bufsize, Int_t splitlevel) |
virtual TFile* | ChangeFile(TFile* file) |
virtual Bool_t | CheckBranchAddressType(TBranch* branch, TClass* ptrClass, EDataType datatype, Bool_t ptr) |
virtual void | TObject::DoError(int level, const char* location, const char* fmt, va_list va) const |
const char* | GetNameByIndex(TString& varexp, Int_t* index, Int_t colindex) const |
virtual void | KeepCircular() |
virtual void | MakeIndex(TString& varexp, Int_t* index) |
void | TObject::MakeZombie() |
TTree
a TTree object has a header with a name and a title.
It consists of a list of independent branches (TBranch). Each branch
has its own definition and list of buffers. Branch buffers may be
automatically written to disk or kept in memory until the Tree attribute
fMaxVirtualSize is reached.
Variables of one branch are written to the same buffer.
A branch buffer is automatically compressed if the file compression
attribute is set (default).
Branches may be written to different files (see TBranch::SetFile).
The ROOT user can decide to make one single branch and serialize one
object into one single I/O buffer or to make several branches.
Making one single branch and one single buffer can be the right choice
when one wants to process only a subset of all entries in the tree.
(you know for example the list of entry numbers you want to process).
Making several branches is particularly interesting in the data analysis
phase, when one wants to histogram some attributes of an object (entry)
without reading all the attributes.
/*
*/
==> TTree *tree = new TTree(name, title)
Creates a Tree with name and title.
Various kinds of branches can be added to a tree:
A - simple structures or list of variables. (may be for C or Fortran structures)
B - any object (inheriting from TObject). (we expect this option be the most frequent)
C - a ClonesArray. (a specialized object for collections of same class objects)
==> Case A
======
TBranch *branch = tree->Branch(branchname,address, leaflist, bufsize)
* address is the address of the first item of a structure
* leaflist is the concatenation of all the variable names and types
separated by a colon character :
The variable name and the variable type are separated by a slash (/).
The variable type may be 0,1 or 2 characters. If no type is given,
the type of the variable is assumed to be the same as the previous
variable. If the first variable does not have a type, it is assumed
of type F by default. The list of currently supported types is given below:
- C : a character string terminated by the 0 character
- B : an 8 bit signed integer (Char_t)
- b : an 8 bit unsigned integer (UChar_t)
- S : a 16 bit signed integer (Short_t)
- s : a 16 bit unsigned integer (UShort_t)
- I : a 32 bit signed integer (Int_t)
- i : a 32 bit unsigned integer (UInt_t)
- F : a 32 bit floating point (Float_t)
- D : a 64 bit floating point (Double_t)
- L : a 64 bit signed integer (Long64_t)
- l : a 64 bit unsigned integer (ULong64_t)
- O : a boolean (Bool_t)
==> Case B
======
TBranch *branch = tree->Branch(branchname,className,object, bufsize, splitlevel)
object is the address of a pointer to an existing object (derived from TObject).
if splitlevel=0, the object is serialized in the branch buffer.
if splitlevel=1 (default), this branch will automatically be split
into subbranches, with one subbranch for each data member or object
of the object itself. In case the object member is a TClonesArray,
the mechanism described in case C is applied to this array.
if splitlevel=2 ,this branch will automatically be split
into subbranches, with one subbranch for each data member or object
of the object itself. In case the object member is a TClonesArray,
it is processed as a TObject*, only one branch.
==> Case C
======
TBranch *branch = tree->Branch(branchname,clonesarray, bufsize, splitlevel)
clonesarray is the address of a pointer to a TClonesArray.
The TClonesArray is a direct access list of objects of the same class.
For example, if the TClonesArray is an array of TTrack objects,
this function will create one subbranch for each data member of
the object TTrack.
==> branch->SetAddress(Void *address)
In case of dynamic structures changing with each entry for example, one must
redefine the branch address before filling the branch again.
This is done via the TBranch::SetAddress member function.
==> tree->Fill()
loops on all defined branches and for each branch invokes the Fill function.
See also the class TNtuple (a simple Tree with branches of floats)
Adding a Branch to an Existing Tree
===================================
You may want to add a branch to an existing tree. For example,
if one variable in the tree was computed with a certain algorithm,
you may want to try another algorithm and compare the results.
One solution is to add a new branch, fill it, and save the tree.
The code below adds a simple branch to an existing tree.
Note the kOverwrite option in the Write method, it overwrites the
existing tree. If it is not specified, two copies of the tree headers
are saved.
void tree3AddBranch(){
TFile f("tree3.root","update");
Float_t new_v;
TTree *t3 = (TTree*)f->Get("t3");
TBranch *newBranch = t3->Branch("new_v",&new_v,"new_v/F");
//read the number of entries in the t3
Long64_t nentries = t3->GetEntries();
for (Long64_t i = 0; i < nentries; i++){
new_v= gRandom->Gaus(0,1);
newBranch->Fill();
}
// save only the new version of the tree
t3->Write("",TObject::kOverwrite);
}
Adding a branch is often not possible because the tree is in a read-only
file and you do not have permission to save the modified tree with the
new branch. Even if you do have the permission, you risk loosing the
original tree with an unsuccessful attempt to save the modification.
Since trees are usually large, adding a branch could extend it over the
2GB limit. In this case, the attempt to write the tree fails, and the
original data is erased.
In addition, adding a branch to a tree enlarges the tree and increases
the amount of memory needed to read an entry, and therefore decreases
the performance.
For these reasons, ROOT offers the concept of friends for trees (and chains).
We encourage you to use TTree::AddFriend rather than adding a branch manually.
/*
*/
=============================================================================
______________________________________________________________________________
*-*-*-*-*-*-*A simple example with histograms and a tree*-*-*-*-*-*-*-*-*-*
*-* ===========================================
This program creates :
- a one dimensional histogram
- a two dimensional histogram
- a profile histogram
- a tree
These objects are filled with some random numbers and saved on a file.
-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*
#include "TFile.h"
#include "TH1.h"
#include "TH2.h"
#include "TProfile.h"
#include "TRandom.h"
#include "TTree.h"
//______________________________________________________________________________
main(int argc, char **argv)
{
// Create a new ROOT binary machine independent file.
// Note that this file may contain any kind of ROOT objects, histograms,trees
// pictures, graphics objects, detector geometries, tracks, events, etc..
// This file is now becoming the current directory.
TFile hfile("htree.root","RECREATE","Demo ROOT file with histograms & trees");
// Create some histograms and a profile histogram
TH1F *hpx = new TH1F("hpx","This is the px distribution",100,-4,4);
TH2F *hpxpy = new TH2F("hpxpy","py ps px",40,-4,4,40,-4,4);
TProfile *hprof = new TProfile("hprof","Profile of pz versus px",100,-4,4,0,20);
// Define some simple structures
typedef struct {Float_t x,y,z;} POINT;
typedef struct {
Int_t ntrack,nseg,nvertex;
UInt_t flag;
Float_t temperature;
} EVENTN;
static POINT point;
static EVENTN eventn;
// Create a ROOT Tree
TTree *tree = new TTree("T","An example of ROOT tree with a few branches");
tree->Branch("point",&point,"x:y:z");
tree->Branch("eventn",&eventn,"ntrack/I:nseg:nvertex:flag/i:temperature/F");
tree->Branch("hpx","TH1F",&hpx,128000,0);
Float_t px,py,pz;
static Float_t p[3];
//--------------------Here we start a loop on 1000 events
for ( Int_t i=0; i<1000; i++) {
gRandom->Rannor(px,py);
pz = px*px + py*py;
Float_t random = gRandom->::Rndm(1);
// Fill histograms
hpx->Fill(px);
hpxpy->Fill(px,py,1);
hprof->Fill(px,pz,1);
// Fill structures
p[0] = px;
p[1] = py;
p[2] = pz;
point.x = 10*(random-1);;
point.y = 5*random;
point.z = 20*random;
eventn.ntrack = Int_t(100*random);
eventn.nseg = Int_t(2*eventn.ntrack);
eventn.nvertex = 1;
eventn.flag = Int_t(random+0.5);
eventn.temperature = 20+random;
// Fill the tree. For each event, save the 2 structures and 3 objects
// In this simple example, the objects hpx, hprof and hpxpy are slightly
// different from event to event. We expect a big compression factor!
tree->Fill();
}
//--------------End of the loop
tree->Print();
// Save all objects in this file
hfile.Write();
// Close the file. Note that this is automatically done when you leave
// the application.
hfile.Close();
return 0;
}
TTree()
-- Default and i/o tree constructor.
Note: We do *not* insert ourself into the current directory.
TTree(const char* name, const char* title, Int_t splitlevel )
-- Normal tree constructor.
The tree is created in the current directory.
Use the various functions Branch below to add branches to this tree.
If the first character of title is a "/", the function assumes a folder name.
In this case, it creates automatically branches following the folder hierarchy.
splitlevel may be used in this case to control the split level.
void AddClone(TTree* clone)
-- Add a cloned tree to our list of trees to be notified whenever we change our branch addresses or when we are deleted.
TFriendElement* AddFriend(const char* treename, const char* filename)
-- Add a TFriendElement to the list of friends.
This function:
-opens a file if filename is specified
-reads a Tree with name treename from the file (current directory)
-adds the Tree to the list of friends
see other AddFriend functions
A TFriendElement TF describes a TTree object TF in a file.
When a TFriendElement TF is added to the the list of friends of an
existing TTree T, any variable from TF can be referenced in a query
to T.
A tree keeps a list of friends. In the context of a tree (or a chain),
friendship means unrestricted access to the friends data. In this way
it is much like adding another branch to the tree without taking the risk
of damaging it. To add a friend to the list, you can use the TTree::AddFriend
method. The tree in the diagram below has two friends (friend_tree1 and
friend_tree2) and now has access to the variables a,b,c,i,j,k,l and m.
/*
*/
TFriendElement* AddFriend(const char* treename, TFile* file)
-- Add a TFriendElement to the list of friends.
The TFile is managed by the user (e.g. the user must delete the file).
For complete description see AddFriend(const char *, const char *).
This function:
-reads a Tree with name treename from the file
-adds the Tree to the list of friends
Long64_t AutoSave(Option_t* option)
-- AutoSave tree header every fAutoSave bytes.
When large Trees are produced, it is safe to activate the AutoSave
procedure. Some branches may have buffers holding many entries.
AutoSave is automatically called by TTree::Fill when the number of bytes
generated since the previous AutoSave is greater than fAutoSave bytes.
This function may also be invoked by the user, for example every
N entries.
Each AutoSave generates a new key on the file.
Once the key with the tree header has been written, the previous cycle
(if any) is deleted.
Note that calling TTree::AutoSave too frequently (or similarly calling
TTree::SetAutoSave with a small value) is an expensive operation.
You should make tests for your own application to find a compromize
between speed and the quantity of information you may loose in case of
a job crash.
In case your program crashes before closing the file holding this tree,
the file will be automatically recovered when you will connect the file
in UPDATE mode.
The Tree will be recovered at the status corresponding to the last AutoSave.
if option contains "SaveSelf", gDirectory->SaveSelf() is called.
This allows another process to analyze the Tree while the Tree is being filled.
By default the previous header is deleted after having written the new header.
if option contains "Overwrite", the previous Tree header is deleted
before written the new header. This option is slightly faster, but
the default option is safer in case of a problem (disk quota exceeded)
when writing the new header.
The function returns the number of bytes written to the file.
if the number of bytes is null, an error has occured while writing
the header to the file.
How to write a Tree in one process and view it from another process
===================================================================
The following two scripts illustrate how to do this.
The script treew.C is executed by process1, treer.C by process2
----- script treew.C
void treew() {
TFile f("test.root","recreate");
TNtuple *ntuple = new TNtuple("ntuple","Demo","px:py:pz:random:i");
Float_t px, py, pz;
for ( Int_t i=0; i<10000000; i++) {
gRandom->Rannor(px,py);
pz = px*px + py*py;
Float_t random = gRandom->Rndm(1);
ntuple->Fill(px,py,pz,random,i);
if (i%1000 == 1) ntuple->AutoSave("SaveSelf");
}
}
----- script treer.C
void treer() {
TFile f("test.root");
TTree *ntuple = (TTree*)f.Get("ntuple");
TCanvas c1;
Int_t first = 0;
while(1) {
if (first == 0) ntuple->Draw("px>>hpx", "","",10000000,first);
else ntuple->Draw("px>>+hpx","","",10000000,first);
first = (Int_t)ntuple->GetEntries();
c1.Update();
gSystem->Sleep(1000); //sleep 1 second
ntuple->Refresh();
}
}
Int_t Branch(TCollection* li, Int_t bufsize , Int_t splitlevel , const char* name )
-- Create one branch for each element in the collection.
Each entry in the collection becomes a top level branch if the
corresponding class is not a collection. If it is a collection, the entry
in the collection becomes in turn top level branches, etc.
The splitlevel is decreased by 1 everytime a new collection is found.
For example if list is a TObjArray*
- if splitlevel = 1, one top level branch is created for each element
of the TObjArray.
- if splitlevel = 2, one top level branch is created for each array element.
if, in turn, one of the array elements is a TCollection, one top level
branch will be created for each element of this collection.
In case a collection element is a TClonesArray, the special Tree constructor
for TClonesArray is called.
The collection itself cannot be a TClonesArray.
The function returns the total number of branches created.
If name is given, all branch names will be prefixed with name_.
IMPORTANT NOTE1: This function should not be called with splitlevel < 1.
IMPORTANT NOTE2: The branches created by this function will have names
corresponding to the collection or object names. It is important
to give names to collections to avoid misleading branch names or
identical branch names. By default collections have a name equal to
the corresponding class name, eg the default name for a TList is "TList".
Example--------------------------------------------------------------:
{
TTree T("T","test list");
TList *l = new TList();
TObjArray *a1 = new TObjArray();
a1->SetName("a1");
l->Add(a1);
TH1F *ha1a = new TH1F("ha1a","ha1",100,0,1);
TH1F *ha1b = new TH1F("ha1b","ha1",100,0,1);
a1->Add(ha1a);
a1->Add(ha1b);
TObjArray *b1 = new TObjArray();
b1->SetName("b1");
l->Add(b1);
TH1F *hb1a = new TH1F("hb1a","hb1",100,0,1);
TH1F *hb1b = new TH1F("hb1b","hb1",100,0,1);
b1->Add(hb1a);
b1->Add(hb1b);
TObjArray *a2 = new TObjArray();
a2->SetName("a2");
l->Add(a2);
TH1S *ha2a = new TH1S("ha2a","ha2",100,0,1);
TH1S *ha2b = new TH1S("ha2b","ha2",100,0,1);
a2->Add(ha2a);
a2->Add(ha2b);
T.Branch(l,16000,2);
T.Print();
}
Int_t Branch(const char* foldername, Int_t bufsize , Int_t splitlevel )
-- Create one branch for each element in the folder.
Returns the total number of branches created.
TBranch* Branch(const char* name, void* address, const char* leaflist, Int_t bufsize )
-- Create a new TTree Branch.
This Branch constructor is provided to support non-objects in
a Tree. The variables described in leaflist may be simple variables
or structures.
See the two following constructors for writing objects in a Tree.
By default the branch buffers are stored in the same file as the Tree.
use TBranch::SetFile to specify a different file
* address is the address of the first item of a structure
or the address of a pointer to an object (see example).
* leaflist is the concatenation of all the variable names and types
separated by a colon character :
The variable name and the variable type are separated by a slash (/).
The variable type may be 0,1 or 2 characters. If no type is given,
the type of the variable is assumed to be the same as the previous
variable. If the first variable does not have a type, it is assumed
of type F by default. The list of currently supported types is given below:
- C : a character string terminated by the 0 character
- B : an 8 bit signed integer (Char_t)
- b : an 8 bit unsigned integer (UChar_t)
- S : a 16 bit signed integer (Short_t)
- s : a 16 bit unsigned integer (UShort_t)
- I : a 32 bit signed integer (Int_t)
- i : a 32 bit unsigned integer (UInt_t)
- F : a 32 bit floating point (Float_t)
- D : a 64 bit floating point (Double_t)
- L : a 64 bit signed integer (Long64_t)
- l : a 64 bit unsigned integer (ULong64_t)
- O : a boolean (Bool_t)
By default, a variable will be copied to the buffer with the number of
bytes specified in the type descriptor character. However, if the type
consists of 2 characters, the second character is an integer that
specifies the number of bytes to be used when copying the variable
to the output buffer. Example:
X ; variable X, type Float_t
Y/I : variable Y, type Int_t
Y/I2 ; variable Y, type Int_t converted to a 16 bits integer
* bufsize is the buffer size in bytes for this branch
The default value is 32000 bytes and should be ok for most cases.
You can specify a larger value (eg 256000) if your Tree is not split
and each entry is large (Megabytes)
A small value for bufsize is optimum if you intend to access
the entries in the Tree randomly and your Tree is in split mode.
TBranch* Branch(const char* name, const char* classname, void* addobj, Int_t bufsize , Int_t splitlevel )
create a new branch with the object of class classname at address addobj.
WARNING:
Starting with Root version 3.01, the Branch function uses the new style
branches (TBranchElement). To get the old behaviour, you can:
- call BranchOld or
- call TTree::SetBranchStyle(0)
Note that with the new style, classname does not need to derive from TObject.
It must derived from TObject if the branch style has been set to 0 (old)
Use splitlevel < 0 instead of splitlevel=0 when the class
has a custom Streamer
Note: if the split level is set to the default (99), TTree::Branch will
not issue a warning if the class can not be split.
TBranch* BranchOld(const char* name, const char* classname, void* addobj, Int_t bufsize , Int_t splitlevel )
-- Create a new TTree BranchObject.
Build a TBranchObject for an object of class classname.
addobj is the address of a pointer to an object of class classname.
IMPORTANT: classname must derive from TObject.
The class dictionary must be available (ClassDef in class header).
This option requires access to the library where the corresponding class
is defined. Accessing one single data member in the object implies
reading the full object.
See the next Branch constructor for a more efficient storage
in case the entry consists of arrays of identical objects.
By default the branch buffers are stored in the same file as the Tree.
use TBranch::SetFile to specify a different file
IMPORTANT NOTE about branch names
In case two or more master branches contain subbranches with
identical names, one must add a "." (dot) character at the end
of the master branch name. This will force the name of the subbranch
to be master.subbranch instead of simply subbranch.
This situation happens when the top level object (say event)
has two or more members referencing the same class.
For example, if a Tree has two branches B1 and B2 corresponding
to objects of the same class MyClass, one can do:
tree.Branch("B1.","MyClass",&b1,8000,1);
tree.Branch("B2.","MyClass",&b2,8000,1);
if MyClass has 3 members a,b,c, the two instructions above will generate
subbranches called B1.a, B1.b ,B1.c, B2.a, B2.b, B2.c
bufsize is the buffer size in bytes for this branch
The default value is 32000 bytes and should be ok for most cases.
You can specify a larger value (eg 256000) if your Tree is not split
and each entry is large (Megabytes)
A small value for bufsize is optimum if you intend to access
the entries in the Tree randomly and your Tree is in split mode.
TBranch* BranchRef()
-- Build the optional branch supporting the TRefTable.
This branch will keep all the information to find the branches
containing referenced objects.
At each Tree::Fill, the branch numbers containing the
referenced objects are saved to the TBranchRef basket.
When the Tree header is saved (via TTree::Write), the branch
is saved keeping the information with the pointers to the branches
having referenced objects.
TBranch* Bronch(const char* name, const char* classname, void* add, Int_t bufsize , Int_t splitlevel )
-- Create a new TTree BranchElement.
WARNING about this new function
===============================
This function is designed to replace the function TTree::Branch above.
This function is far more powerful than the Branch function.
It supports the full C++, including STL and has the same behaviour
in split or non-split mode. classname does not have to derive from TObject.
The function is based on the new TStreamerInfo.
Build a TBranchElement for an object of class classname.
addobj is the address of a pointer to an object of class classname.
The class dictionary must be available (ClassDef in class header).
This option requires access to the library where the corresponding class
is defined. Accessing one single data member in the object implies
reading the full object.
By default the branch buffers are stored in the same file as the Tree.
use TBranch::SetFile to specify a different file
IMPORTANT NOTE about branch names
In case two or more master branches contain subbranches with
identical names, one must add a "." (dot) character at the end
of the master branch name. This will force the name of the subbranch
to be master.subbranch instead of simply subbranch.
This situation happens when the top level object (say event)
has two or more members referencing the same class.
For example, if a Tree has two branches B1 and B2 corresponding
to objects of the same class MyClass, one can do:
tree.Branch("B1.","MyClass",&b1,8000,1);
tree.Branch("B2.","MyClass",&b2,8000,1);
if MyClass has 3 members a,b,c, the two instructions above will generate
subbranches called B1.a, B1.b ,B1.c, B2.a, B2.b, B2.c
bufsize is the buffer size in bytes for this branch
The default value is 32000 bytes and should be ok for most cases.
You can specify a larger value (eg 256000) if your Tree is not split
and each entry is large (Megabytes)
A small value for bufsize is optimum if you intend to access
the entries in the Tree randomly and your Tree is in split mode.
Use splitlevel < 0 instead of splitlevel=0 when the class
has a custom Streamer
Note: if the split level is set to the default (99), TTree::Branch will
not issue a warning if the class can not be split.
Int_t BuildIndex(const char* majorname, const char* minorname )
-- Build a Tree Index (default is TTreeIndex).
See a description of the parameters and functionality in
TTreeIndex::TTreeIndex().
The return value is the number of entries in the Index (< 0 indicates failure).
A TTreeIndex object pointed by fTreeIndex is created.
This object will be automatically deleted by the TTree destructor.
See also comments in TTree::SetTreeIndex().
TFile* ChangeFile(TFile* file)
-- Called by TTree::Fill() when file has reached its maximum fgMaxTreeSize.
Create a new file. If the original file is named "myfile.root",
subsequent files are named "myfile_1.root", "myfile_2.root", etc.
Returns a pointer to the new file.
Currently, the automatic change of file is restricted
to the case where the tree is in the top level directory.
The file should not contain sub-directories.
Before switching to a new file, the tree header is written
to the current file, then the current file is closed.
To process the multiple files created by ChangeFile, one must use
a TChain.
The new file name has a suffix "_N" where N is equal to fFileNumber+1.
By default a Root session starts with fFileNumber=0. One can set
fFileNumber to a different value via TTree::SetFileNumber.
In case a file named "_N" already exists, the function will try
a file named "__N", then "___N", etc.
fgMaxTreeSize can be set via the static function TTree::SetMaxTreeSize.
The default value of fgMaxTreeSize is 1.9 Gigabytes.
If the current file contains other objects like TH1 and TTree,
these objects are automatically moved to the new file.
IMPORTANT NOTE:
Be careful when writing the final Tree header to the file!
Don't do:
TFile *file = new TFile("myfile.root","recreate");
TTree *T = new TTree("T","title");
T->Fill(); //loop
file->Write();
file->Close();
but do the following:
TFile *file = new TFile("myfile.root","recreate");
TTree *T = new TTree("T","title");
T->Fill(); //loop
file = T->GetCurrentFile(); //to get the pointer to the current file
file->Write();
file->Close();
TTree* CloneTree(Long64_t nentries , Option_t* option )
-- Create a clone of this tree and copy nentries.
By default copy all entries.
Note that only active branches are copied.
The compression level of the cloned tree is set to the destination file's
compression level.
IMPORTANT: The cloned tree stays connected with this tree until this tree
is deleted. In particular, any changes in branch addresses
in this tree are forwarded to the clone trees, unless a branch
in a clone tree has had its address changed, in which case
that change stays in effect. When this tree is deleted, all the
addresses of the cloned tree are reset to their default values.
If 'option' contains the word 'fast' and nentries is -1 and no branch
is disabled, the clone will be done without unzipping or unstreaming
the baskets (i.e., a direct copy of the raw bytes on disk).
When 'fast' is specified, 'option' can also contains a
sorting order for the baskets in the output file.
There is currently 3 supported sorting order:
SortBasketsByOffset (the default)
SortBasketsByBranch
SortBasketsByEntry
When using SortBasketsByOffset the baskets are written in
the output file in the same order as in the original file
(i.e. the basket are sorted on their offset in the original
file; Usually this also means that the baskets are sorted
on the index/number of the _last_ entry they contain)
When using SortBasketsByBranch all the baskets of each
individual branches are stored contiguously. This tends to
optimize reading speed when reading a small number (1->5) of
branches, since all their baskets will be clustered together
instead of being spread across the file. However it might
decrease the performance when reading more branches (or the full
entry).
When using SortBasketsByEntry the baskets with the lowest
starting entry are written first. (i.e. the baskets are
sorted on the index/number of the first entry they contain).
This means that on the file the baskets will be in the order
in which they will be needed when reading the whole tree
sequentially.
For examples of CloneTree, see tutorials:
-- copytree
A macro to copy a subset of a TTree to a new TTree.
The input file has been generated by the program in $ROOTSYS/test/Event
with: Event 1000 1 1 1
-- copytree2
A macro to copy a subset of a TTree to a new TTree.
One branch of the new Tree is written to a separate file.
The input file has been generated by the program in $ROOTSYS/test/Event
with: Event 1000 1 1 1
TTree* CopyTree(const char* selection, Option_t* option , Long64_t nentries , Long64_t firstentry )
-- Copy a tree with selection.
IMPORTANT:
The returned copied tree stays connected with the original tree
until the original tree is deleted. In particular, any changes
to the branch addresses in the original tree are also made to
the copied tree. Any changes made to the branch addresses of the
copied tree are overridden anytime the original tree changes its
branch addresses. When the original tree is deleted, all the
branch addresses of the copied tree are set to zero.
For examples of CopyTree, see the tutorials:
-- copytree
Example macro to copy a subset of a tree to a new tree.
The input file was generated by running the program in
$ROOTSYS/test/Event in this way:
./Event 1000 1 1 1
-- copytree2
Example macro to copy a subset of a tree to a new tree.
One branch of the new tree is written to a separate file.
The input file was generated by running the program in
$ROOTSYS/test/Event in this way:
./Event 1000 1 1 1
-- copytree3
Example macro to copy a subset of a tree to a new tree.
Only selected entries are copied to the new tree.
NOTE that only the active branches are copied.
void Delete(Option_t* option )
-- Delete this tree from memory or/and disk.
if option == "all" delete Tree object from memory AND from disk
all baskets on disk are deleted. All keys with same name
are deleted.
if option =="" only Tree object in memory is deleted.
Long64_t Draw(const char* varexp, const TCut& selection, Option_t* option, Long64_t nentries, Long64_t firstentry)
Draw expression varexp for specified entries.
Returns -1 in case of error or number of selected events in case of success.
This function accepts TCut objects as arguments.
Useful to use the string operator +
example:
ntuple.Draw("x",cut1+cut2+cut3);
Long64_t Draw(const char* varexp, const char* selection, Option_t* option, Long64_t nentries, Long64_t firstentry)
Draw expression varexp for specified entries.
Returns -1 in case of error or number of selected events in case of success.
varexp is an expression of the general form
- "e1" produces a 1-d histogram (TH1F) of expression "e1"
- "e1:e2" produces an unbinned 2-d scatter-plot (TGraph) of "e1" versus "e2"
- "e1:e2:e3" produces an unbinned 3-d scatter-plot (TPolyMarker3D) of "e1"
versus "e2" versus "e3"
- "e1:e2:e3:e4" produces an unbinned 3-d scatter-plot (TPolyMarker3D) of "e1"
versus "e2" versus "e3" and "e4" mapped on the color number.
(to create histograms in the 2, 3, and 4 dimesional case, see section "Saving
the result of Draw to an histogram")
Example:
varexp = x simplest case: draw a 1-Dim distribution of column named x
= sqrt(x) : draw distribution of sqrt(x)
= x*y/z
= y:sqrt(x) 2-Dim distribution of y versus sqrt(x)
= px:py:pz:2.5*E produces a 3-d scatter-plot of px vs py ps pz
and the color number of each marker will be 2.5*E.
If the color number is negative it is set to 0.
If the color number is greater than the current number of colors
it is set to the highest color number.
The default number of colors is 50.
see TStyle::SetPalette for setting a new color palette.
Note that the variables e1, e2 or e3 may contain a selection.
example, if e1= x*(y<0), the value histogrammed will be x if y<0
and will be 0 otherwise.
selection is an expression with a combination of the columns.
In a selection all the C++ operators are authorized.
The value corresponding to the selection expression is used as a weight
to fill the histogram.
If the expression includes only boolean operations, the result
is 0 or 1. If the result is 0, the histogram is not filled.
In general, the expression may be of the form:
value*(boolean expression)
if boolean expression is true, the histogram is filled with
a weight = value.
Examples:
selection1 = "x<y && sqrt(z)>3.2"
selection2 = "(x+y)*(sqrt(z)>3.2)"
selection1 returns a weigth = 0 or 1
selection2 returns a weight = x+y if sqrt(z)>3.2
returns a weight = 0 otherwise.
option is the drawing option.
- See TH1::Draw for the list of all drawing options.
- If option COL is specified when varexp has three fields:
tree.Draw("e1:e2:e3","","col");
a 2D scatter is produced with e1 vs e2, and e3 is mapped on the color
table.
- If option contains the string "goff", no graphics is generated.
nentries is the number of entries to process (default is all)
first is the first entry to process (default is 0)
This function returns the number of selected entries. It returns -1
if an error occurs.
Drawing expressions using arrays and array elements
===================================================
Let assumes, a leaf fMatrix, on the branch fEvent, which is a 3 by 3 array,
or a TClonesArray.
In a TTree::Draw expression you can now access fMatrix using the following
syntaxes:
String passed What is used for each entry of the tree
"fMatrix" the 9 elements of fMatrix
"fMatrix[][]" the 9 elements of fMatrix
"fMatrix[2][2]" only the elements fMatrix[2][2]
"fMatrix[1]" the 3 elements fMatrix[1][0], fMatrix[1][1] and fMatrix[1][2]
"fMatrix[1][]" the 3 elements fMatrix[1][0], fMatrix[1][1] and fMatrix[1][2]
"fMatrix[][0]" the 3 elements fMatrix[0][0], fMatrix[1][0] and fMatrix[2][0]
"fEvent.fMatrix...." same as "fMatrix..." (unless there is more than one leaf named fMatrix!).
In summary, if a specific index is not specified for a dimension, TTree::Draw
will loop through all the indices along this dimension. Leaving off the
last (right most) dimension of specifying then with the two characters '[]'
is equivalent. For variable size arrays (and TClonesArray) the range
of the first dimension is recalculated for each entry of the tree.
TTree::Draw also now properly handling operations involving 2 or more arrays.
Let assume a second matrix fResults[5][2], here are a sample of some
of the possible combinations, the number of elements they produce and
the loop used:
expression element(s) Loop
"fMatrix[2][1] - fResults[5][2]" one no loop
"fMatrix[2][] - fResults[5][2]" three on 2nd dim fMatrix
"fMatrix[2][] - fResults[5][]" two on both 2nd dimensions
"fMatrix[][2] - fResults[][1]" three on both 1st dimensions
"fMatrix[][2] - fResults[][]" six on both 1st and 2nd dimensions of
fResults
"fMatrix[][2] - fResults[3][]" two on 1st dim of fMatrix and 2nd of
fResults (at the same time)
"fMatrix[][] - fResults[][]" six on 1st dim then on 2nd dim
In summary, TTree::Draw loops through all un-specified dimensions. To
figure out the range of each loop, we match each unspecified dimension
from left to right (ignoring ALL dimensions for which an index has been
specified), in the equivalent loop matched dimensions use the same index
and are restricted to the smallest range (of only the matched dimensions).
When involving variable arrays, the range can of course be different
for each entry of the tree.
So the loop equivalent to "fMatrix[][2] - fResults[3][]" is:
for (Int_t i0; i < min(3,2); i++) {
use the value of (fMatrix[i0][2] - fMatrix[3][i0])
}
So the loop equivalent to "fMatrix[][2] - fResults[][]" is:
for (Int_t i0; i < min(3,5); i++) {
for (Int_t i1; i1 < 2; i1++) {
use the value of (fMatrix[i0][2] - fMatrix[i0][i1])
}
}
So the loop equivalent to "fMatrix[][] - fResults[][]" is:
for (Int_t i0; i < min(3,5); i++) {
for (Int_t i1; i1 < min(3,2); i1++) {
use the value of (fMatrix[i0][i1] - fMatrix[i0][i1])
}
}
Retrieving the result of Draw
=============================
By default the temporary histogram created is called "htemp", but only in
the one dimensional Draw("e1") it contains the TTree's data points. For
a two dimensional Draw, the data is filled into a TGraph which is named
"Graph". They can be retrieved by calling
TH1F *htemp = (TH1F*)gPad->GetPrimitive("htemp"); // 1D
TGraph *graph = (TGraph*)gPad->GetPrimitive("Graph"); // 2D
For a three and four dimensional Draw the TPloyMarker3D is unnamed, and
cannot be retrieved.
gPad always contains a TH1 derived object called "htemp" which allows to
access the axes:
TGraph *graph = (TGraph*)gPad->GetPrimitive("Graph"); // 2D
TH2F *htemp = (TH2F*)gPad->GetPrimitive("htemp"); // empty, but has axes
TAxis *xaxis = htemp->GetXaxis();
Saving the result of Draw to an histogram
=========================================
If varexp0 contains >>hnew (following the variable(s) name(s),
the new histogram created is called hnew and it is kept in the current
directory (and also the current pad). This works for all dimensions.
Example:
tree.Draw("sqrt(x)>>hsqrt","y>0")
will draw sqrt(x) and save the histogram as "hsqrt" in the current
directory. To retrieve it do:
TH1F *hsqrt = (TH1F*)gDirectory->Get("hsqrt");
The binning information is taken from the environment variables
Hist.Binning.?D.?
In addition, the name of the histogram can be followed by up to 9
numbers between '(' and ')', where the numbers describe the
following:
1 - bins in x-direction
2 - lower limit in x-direction
3 - upper limit in x-direction
4-6 same for y-direction
7-9 same for z-direction
When a new binning is used the new value will become the default.
Values can be skipped.
Example:
tree.Draw("sqrt(x)>>hsqrt(500,10,20)")
// plot sqrt(x) between 10 and 20 using 500 bins
tree.Draw("sqrt(x):sin(y)>>hsqrt(100,10,60,50,.1,.5)")
// plot sqrt(x) against sin(y)
// 100 bins in x-direction; lower limit on x-axis is 10; upper limit is 60
// 50 bins in y-direction; lower limit on y-axis is .1; upper limit is .5
By default, the specified histogram is reset.
To continue to append data to an existing histogram, use "+" in front
of the histogram name.
A '+' in front of the histogram name is ignored, when the name is followed by
binning information as described in the previous paragraph.
tree.Draw("sqrt(x)>>+hsqrt","y>0")
will not reset hsqrt, but will continue filling.
This works for 1-D, 2-D and 3-D histograms.
Accessing collection objects
============================
TTree::Draw default's handling of collections is to assume that any
request on a collection pertain to it content. For example, if fTracks
is a collection of Track objects, the following:
tree->Draw("event.fTracks.fPx");
will plot the value of fPx for each Track objects inside the collection.
Also
tree->Draw("event.fTracks.size()");
would plot the result of the member function Track::size() for each
Track object inside the collection.
To access information about the collection itself, TTree::Draw support
the '@' notation. If a variable which points to a collection is prefixed
or postfixed with '@', the next part of the expression will pertain to
the collection object. For example:
tree->Draw("event.@fTracks.size()");
will plot the size of the collection refered to by fTracks (i.e the number
of Track objects).
Drawing 'objects'
=================
When a class has a member function named AsDouble or AsString, requesting
to directly draw the object will imply a call to one of the 2 functions.
If both AsDouble and AsString are present, AsDouble will be used.
AsString can return either a char*, a std::string or a TString.s
For example, the following
tree->Draw("event.myTTimeStamp");
will draw the same histogram as
tree->Draw("event.myTTimeStamp.AsDouble()");
In addition, when the object is a type TString or std::string, TTree::Draw
will call respectively TString::Data and std::string::c_str()
If the object is a TBits, the histogram will contain the index of the bit
that are turned on.
Special functions and variables
===============================
Entry$: A TTree::Draw formula can use the special variable Entry$
to access the entry number being read. For example to draw every
other entry use:
tree.Draw("myvar","Entry$%2==0");
Entry$ : return the current entry number (== TTree::GetReadEntry())
Entries$ : return the total number of entries (== TTree::GetEntries())
Length$ : return the total number of element of this formula for this
entry (==TTreeFormula::GetNdata())
Iteration$: return the current iteration over this formula for this
entry (i.e. varies from 0 to Length$).
Length$(formula): return the total number of element of the formula given as a
parameter.
Sum$(formula): return the sum of the value of the elements of the formula given
as a parameter. For eaxmple the mean for all the elements in
one entry can be calculated with:
Sum$(formula)/Length$(formula)
Alt$(primary,alternate) : return the value of "primary" if it is available
for the current iteration otherwise return the value of "alternate".
For example, with arr1[3] and arr2[2]
tree->Draw("arr1+Alt$(arr2,0)");
will draw arr1[0]+arr2[0] ; arr1[1]+arr2[1] and arr1[2]+0
Or with a variable size array arr3
tree->Draw("Alt$(arr3[0],0)+Alt$(arr3[1],0)+Alt$(arr3[2],0)");
will draw the sum arr3 for the index 0 to min(2,actual_size_of_arr3-1)
As a comparison
tree->Draw("arr3[0]+arr3[1]+arr3[2]");
will draw the sum arr3 for the index 0 to 2 only if the
actual_size_of_arr3 is greater or equal to 3.
Note that the array in 'primary' is flatened/linearilized thus using
Alt$ with multi-dimensional arrays of different dimensions in unlikely
to yield the expected results. To visualize a bit more what elements
would be matched by TTree::Draw, TTree::Scan can be used:
tree->Scan("arr1:Alt$(arr2,0)");
will print on one line the value of arr1 and (arr2,0) that will be
matched by
tree->Draw("arr1-Alt$(arr2,0)");
Drawing a user function accessing the TTree data directly
=========================================================
If the formula contains a file name, TTree::MakeProxy will be used
to load and execute this file. In particular it will draw the
result of a function with the same name as the file. The function
will be executed in a context where the name of the branches can
be used as a C++ variable.
For example draw px using the file hsimple.root (generated by the
hsimple.C tutorial), we need a file named hsimple.cxx:
double hsimple() {
return px;
}
MakeProxy can then be used indirectly via the TTree::Draw interface
as follow:
new TFile("hsimple.root")
ntuple->Draw("hsimple.cxx");
A more complete example is available in the tutorials directory:
h1analysisProxy.cxx , h1analysProxy.h and h1analysisProxyCut.C
which reimplement the selector found in h1analysis.C
The main features of this facility are:
* on-demand loading of branches
* ability to use the 'branchname' as if it was a data member
* protection against array out-of-bound
* ability to use the branch data as object (when the user code is available)
See TTree::MakeProxy for more details.
Making a Profile histogram
==========================
In case of a 2-Dim expression, one can generate a TProfile histogram
instead of a TH2F histogram by specyfying option=prof or option=profs.
The option=prof is automatically selected in case of y:x>>pf
where pf is an existing TProfile histogram.
Saving the result of Draw to a TEventList
=========================================
TTree::Draw can be used to fill a TEventList object (list of entry numbers)
instead of histogramming one variable.
If varexp0 has the form >>elist , a TEventList object named "elist"
is created in the current directory. elist will contain the list
of entry numbers satisfying the current selection.
Example:
tree.Draw(">>yplus","y>0")
will create a TEventList object named "yplus" in the current directory.
In an interactive session, one can type (after TTree::Draw)
yplus.Print("all")
to print the list of entry numbers in the list.
By default, the specified entry list is reset.
To continue to append data to an existing list, use "+" in front
of the list name;
tree.Draw(">>+yplus","y>0")
will not reset yplus, but will enter the selected entries at the end
of the existing list.
Using a TEventList as Input
===========================
Once a TEventList object has been generated, it can be used as input
for TTree::Draw. Use TTree::SetEventList to set the current event list
Example:
TEventList *elist = (TEventList*)gDirectory->Get("yplus");
tree->SetEventList(elist);
tree->Draw("py");
If arrays are used in the selection critera, the entry entered in the
list are all the entries that have at least one element of the array that
satisfy the selection.
Example:
tree.Draw(">>pyplus","fTracks.fPy>0");
tree->SetEventList(pyplus);
tree->Draw("fTracks.fPy");
will draw the fPy of ALL tracks in event with at least one track with
a positive fPy.
To select only the elements that did match the original selection
use TEventList::SetReapplyCut.
Example:
tree.Draw(">>pyplus","fTracks.fPy>0");
pyplus->SetReapplyCut(kTRUE);
tree->SetEventList(pyplus);
tree->Draw("fTracks.fPy");
will draw the fPy of only the tracks that have a positive fPy.
Note: Use tree->SetEventList(0) if you do not want use the list as input.
How to obtain more info from TTree::Draw
========================================
Once TTree::Draw has been called, it is possible to access useful
information still stored in the TTree object via the following functions:
-GetSelectedRows() // return the number of entries accepted by the
//selection expression. In case where no selection
//was specified, returns the number of entries processed.
-GetV1() //returns a pointer to the double array of V1
-GetV2() //returns a pointer to the double array of V2
-GetV3() //returns a pointer to the double array of V3
-GetW() //returns a pointer to the double array of Weights
//where weight equal the result of the selection expression.
where V1,V2,V3 correspond to the expressions in
TTree::Draw("V1:V2:V3",selection);
Example:
Root > ntuple->Draw("py:px","pz>4");
Root > TGraph *gr = new TGraph(ntuple->GetSelectedRows(),
ntuple->GetV2(), ntuple->GetV1());
Root > gr->Draw("ap"); //draw graph in current pad
creates a TGraph object with a number of points corresponding to the
number of entries selected by the expression "pz>4", the x points of the graph
being the px values of the Tree and the y points the py values.
Important note: By default TTree::Draw creates the arrays obtained
with GetV1, GetV2, GetV3, GetW with a length corresponding to the
parameter fEstimate. By default fEstimate=10000 and can be modified
via TTree::SetEstimate. A possible recipee is to do
tree->SetEstimate(tree->GetEntries());
You must call SetEstimate if the expected number of selected rows
is greater than 10000.
You can use the option "goff" to turn off the graphics output
of TTree::Draw in the above example.
Automatic interface to TTree::Draw via the TTreeViewer
======================================================
A complete graphical interface to this function is implemented
in the class TTreeViewer.
To start the TTreeViewer, three possibilities:
- select TTree context menu item "StartViewer"
- type the command "TTreeViewer TV(treeName)"
- execute statement "tree->StartViewer();"
void DropBuffers(Int_t)
-- Drop branch buffers to accomodate nbytes below MaxVirtualsize.
Int_t Fill()
-- Fill all branches.
This function loops on all the branches of this tree. For
each branch, it copies to the branch buffer (basket) the current
values of the leaves data types. If a leaf is a simple data type,
a simple conversion to a machine independent format has to be done.
The function returns the number of bytes committed to the
individual branches.
If a write error occurs, the number of bytes returned is -1.
If no data are written, because, e.g., the branch is disabled,
the number of bytes returned is 0.
TLeaf* FindLeaf(const char* searchname)
-- FIXME: Describe this function.
Long64_t Fit(const char* funcname, const char* varexp, const char* selection, Option_t* option, Option_t* goption, Long64_t nentries, Long64_t firstentry)
-- Fit a projected item(s) from a tree.
funcname is a TF1 function.
See TTree::Draw() for explanations of the other parameters.
By default the temporary histogram created is called htemp.
If varexp contains >>hnew , the new histogram created is called hnew
and it is kept in the current directory.
The function returns the number of selected entries.
Example:
tree.Fit(pol4,sqrt(x)>>hsqrt,y>0)
will fit sqrt(x) and save the histogram as "hsqrt" in the current
directory.
See also TTree::UnbinnedFit
const char* GetAlias(const char* aliasName)
-- Returns the expanded value of the alias. Search in the friends if any.
TBranch* GetBranch(const char* name)
-- Return pointer to the branch with the given name in this tree or its friends.
Bool_t GetBranchStatus(const char* branchname)
-- Return status of branch with name branchname.
0 if branch is not activated
1 if branch is activated
Long64_t GetEntries(const char *selection)
Return the number of entries matching the selection.
Return -1 in case of errors.
If the selection uses any arrays or containers, we return the number
of entries where at least one element match the selection.
GetEntries is implemented using the selector class TSelectorEntries,
which can be used directly (see code in TTreePlayer::GetEntries) for
additional option.
If SetEventList was used on the TTree or TChain, only that subset
of entries will be considered.
Long64_t GetEntriesFriend()
-- Return number of entries of this tree if not zero, otherwise return the number of entries in the first friend tree.
Int_t GetEntry(Long64_t entry, Int_t getall)
-- Read all branches of entry and return total number of bytes read.
getall = 0 : get only active branches
getall = 1 : get all branches
The function returns the number of bytes read from the input buffer.
If entry does not exist the function returns 0.
If an I/O error occurs, the function returns -1.
If the Tree has friends, also read the friends entry
To activate/deactivate one or more branches, use TBranch::SetBranchStatus
For example, if you have a Tree with several hundred branches, and you
are interested only by branches named "u" and "v", do
mytree.SetBranchStatus("*",0); //disable all branches
mytree.SetBranchStatus("a",1);
mytree.SetBranchStatus("b",1);
when calling mytree.GetEntry(i); only branches "a" and "b" will be read.
WARNING!!
If your Tree has been created in split mode with a parent branch "parent",
mytree.SetBranchStatus("parent",1);
will not activate the sub-branches of "parent". You should do:
mytree.SetBranchStatus("parent*",1);
An alternative is to call directly
brancha.GetEntry(i)
branchb.GetEntry(i);
IMPORTANT NOTE
==============
By default, GetEntry reuses the space allocated by the previous object
for each branch. You can force the previous object to be automatically
deleted if you call mybranch.SetAutoDelete(kTRUE) (default is kFALSE).
Example:
Consider the example in $ROOTSYS/test/Event.h
The top level branch in the tree T is declared with:
Event *event = 0; //event must be null or point to a valid object
//it must be initialized
T.SetBranchAddress("event",&event);
When reading the Tree, one can choose one of these 3 options:
OPTION 1
--------
for (Long64_t i=0;i<nentries;i++) {
T.GetEntry(i);
// the object event has been filled at this point
}
The default (recommended). At the first entry an object of the
class Event will be created and pointed by event.
At the following entries, event will be overwritten by the new data.
All internal members that are TObject* are automatically deleted.
It is important that these members be in a valid state when GetEntry
is called. Pointers must be correctly initialized.
However these internal members will not be deleted if the characters "->"
are specified as the first characters in the comment field of the data
member declaration.
If "->" is specified, the pointer member is read via pointer->Streamer(buf).
In this case, it is assumed that the pointer is never null (case
of pointer TClonesArray *fTracks in the Event example).
If "->" is not specified, the pointer member is read via buf >> pointer.
In this case the pointer may be null. Note that the option with "->"
is faster to read or write and it also consumes less space in the file.
OPTION 2
--------
The option AutoDelete is set
TBranch *branch = T.GetBranch("event");
branch->SetAddress(&event);
branch->SetAutoDelete(kTRUE);
for (Long64_t i=0;i<nentries;i++) {
T.GetEntry(i);
// the objrect event has been filled at this point
}
In this case, at each iteration, the object event is deleted by GetEntry
and a new instance of Event is created and filled.
OPTION 3
--------
Same as option 1, but you delete yourself the event.
for (Long64_t i=0;i<nentries;i++) {
delete event;
event = 0; // EXTREMELY IMPORTANT
T.GetEntry(i);
// the objrect event has been filled at this point
}
It is strongly recommended to use the default option 1. It has the
additional advantage that functions like TTree::Draw (internally
calling TTree::GetEntry) will be functional even when the classes in the
file are not available.
Long64_t GetEntryNumber(Long64_t entry)
-- Return entry number corresponding to entry.
if no selection list returns entry
else returns the entry number corresponding to the list index=entry
Long64_t GetEntryNumberWithBestIndex(Int_t major, Int_t minor)
-- Return entry number corresponding to major and minor number.
Note that this function returns only the entry number, not the data
To read the data corresponding to an entry number, use TTree::GetEntryWithIndex
the BuildIndex function has created a table of Long64_t* of sorted values
corresponding to val = major<<31 + minor;
The function performs binary search in this sorted table.
If it finds a pair that maches val, it returns directly the
index in the table.
If an entry corresponding to major and minor is not found, the function
returns the index of the major,minor pair immediatly lower than the
requested value, ie it will return -1 if the pair is lower than
the first entry in the index.
See also GetEntryNumberWithIndex
Long64_t GetEntryNumberWithIndex(Int_t major, Int_t minor)
-- Return entry number corresponding to major and minor number.
Note that this function returns only the entry number, not the data
To read the data corresponding to an entry number, use TTree::GetEntryWithIndex
the BuildIndex function has created a table of Long64_t* of sorted values
corresponding to val = major<<31 + minor;
The function performs binary search in this sorted table.
If it finds a pair that maches val, it returns directly the
index in the table, otherwise it returns -1.
See also GetEntryNumberWithBestIndex
Int_t GetEntryWithIndex(Int_t major, Int_t minor)
-- Read entry corresponding to major and minor number.
The function returns the total number of bytes read.
If the Tree has friend trees, the corresponding entry with
the index values (major,minor) is read. Note that the master Tree
and its friend may have different entry serial numbers corresponding
to (major,minor).
const char* GetFriendAlias(TTree* tree)
-- If the the 'tree' is a friend, this method returns its alias name.
This alias is an alternate name for the tree.
It can be used in conjunction with a branch or leaf name in a TTreeFormula,
to specify in which particular tree the branch or leaf can be found if
the friend trees have branches or leaves with the same name as the master
tree.
It can also be used in conjunction with an alias created using
TTree::SetAlias in a TTreeFormula, e.g.:
maintree->Draw("treealias.fPx - treealias.myAlias");
where fPx is a branch of the friend tree aliased as 'treealias' and 'myAlias'
was created using TTree::SetAlias on the friend tree.
However, note that 'treealias.myAlias' will be expanded literally,
without remembering that it comes from the aliased friend and thus
the branch name might not be disambiguated properly, which means
that you may not be able to take advantage of this feature.
TLeaf* GetLeaf(const char* aname)
-- Return pointer to the 1st Leaf named name in any Branch of this Tree or any branch in the list of friend trees.
aname may be of the form branchname/leafname
Double_t GetMaximum(const char* columname)
-- Return maximum of column with name columname.
Double_t GetMinimum(const char* columname)
-- Return minimum of column with name columname.
const char* GetNameByIndex(TString& varexp, Int_t* index, Int_t colindex)
-- Return name corresponding to colindex in varexp.
varexp is a string of names separated by :
index is an array with pointers to the start of name[i] in varexp
TList* GetUserInfo()
-- Return a pointer to the list containing user objects associated to this tree.
The list is automatically created if it does not exist.
WARNING: By default the TTree destructor will delete all objects added
to this list. If you do not want these objects to be deleted,
call:
mytree->GetUserInfo()->Clear();
before deleting the tree.
Int_t LoadBaskets(Long64_t maxmemory)
-- Read in memory all baskets from all branches up to the limit of maxmemory bytes.
If maxmemory is non null and positive SetMaxVirtualSize is called
with this value. Default for maxmemory is 2000000000 (2 Gigabytes).
The function returns the total number of baskets read into memory
if negative an error occured while loading the branches.
This method may be called to force branch baskets in memory
when random access to branch entries is required.
If random access to only a few branches is required, you should
call directly TBranch::LoadBaskets.
Long64_t LoadTreeFriend(Long64_t entry, TTree* masterTree)
-- Load entry on behalf of our master tree, we may use an index.
Called by LoadTree() when the masterTree looks for the entry
number in a friend tree (us) corresponding to the passed entry
number in the masterTree.
If we have no index, our entry number and the masterTree entry
number are the same.
If we *do* have an index, we must find the (major, minor) value pair
in masterTree to locate our corresponding entry.
Int_t MakeClass(const char* classname, Option_t* option)
-- Generate a skeleton analysis class for this tree.
The following files are produced: classname.h and classname.C.
If classname is 0, classname will be called "nameoftree".
The generated code in classname.h includes the following:
- Identification of the original tree and the input file name.
- Definition of an analysis class (data members and member functions).
- The following member functions:
- constructor (by default opening the tree file),
- GetEntry(Long64_t entry),
- Init(TTree* tree) to initialize a new TTree,
- Show(Long64_t entry) to read and dump entry.
The generated code in classname.C includes only the main
analysis function Loop.
To use this function:
- Open your tree file (eg: TFile f("myfile.root");)
- T->MakeClass("MyClass");
where T is the name of the TTree in file myfile.root,
and MyClass.h, MyClass.C the name of the files created by this function.
In a ROOT session, you can do:
root > .L MyClass.C
root > MyClass* t = new MyClass;
root > t->GetEntry(12); // Fill data members of t with entry number 12.
root > t->Show(); // Show values of entry 12.
root > t->Show(16); // Read and show values of entry 16.
root > t->Loop(); // Loop on all entries.
NOTE: Do not use the code generated for a single TTree which is part
of a TChain to process that entire TChain. The maximum dimensions
calculated for arrays on the basis of a single TTree from the TChain
might be (will be!) too small when processing all of the TTrees in
the TChain. You must use myChain.MakeClass() to generate the code,
not myTree.MakeClass(...).
Int_t MakeCode(const char* filename)
-- Generate a skeleton function for this tree.
The function code is written on filename.
If filename is 0, filename will be called nameoftree.C
The generated code includes the following:
- Identification of the original Tree and Input file name,
- Opening the Tree file,
- Declaration of Tree variables,
- Setting of branches addresses,
- A skeleton for the entry loop.
To use this function:
- Open your Tree file (eg: TFile f("myfile.root");)
- T->MakeCode("MyAnalysis.C");
where T is the name of the TTree in file myfile.root
and MyAnalysis.C the name of the file created by this function.
NOTE: Since the implementation of this function, a new and better
function TTree::MakeClass() has been developed.
Int_t MakeProxy(const char* proxyClassname, const char* macrofilename, const char* cutfilename, const char* option, Int_t maxUnrolling)
-- Generate a skeleton analysis class for this Tree using TBranchProxy.
TBranchProxy is the base of a class hierarchy implementing an
indirect access to the content of the branches of a TTree.
"proxyClassname" is expected to be of the form:
[path/]fileprefix
The skeleton will then be generated in the file:
fileprefix.h
located in the current directory or in 'path/' if it is specified.
The class generated will be named 'fileprefix'
"macrofilename" and optionally "cutfilename" are expected to point
to source files which will be included by the generated skeleton.
Method of the same name as the file(minus the extension and path)
will be called by the generated skeleton's Process method as follow:
[if (cutfilename())] htemp->Fill(macrofilename());
"option" can be used select some of the optional features during
the code generation. The possible options are:
nohist : indicates that the generated ProcessFill should not
fill the histogram.
'maxUnrolling' controls how deep in the class hierachy does the
system 'unroll' classes that are not split. Unrolling a class
allows direct access to its data members (this emulates the behavior
of TTreeFormula).
The main features of this skeleton are:
* on-demand loading of branches
* ability to use the 'branchname' as if it was a data member
* protection against array out-of-bounds errors
* ability to use the branch data as an object (when the user code is available)
For example with Event.root, if
Double_t somePx = fTracks.fPx[2];
is executed by one of the method of the skeleton,
somePx will updated with the current value of fPx of the 3rd track.
Both macrofilename and the optional cutfilename are expected to be
the name of source files which contain at least a free standing
function with the signature:
x_t macrofilename(); // i.e function with the same name as the file
and
y_t cutfilename(); // i.e function with the same name as the file
x_t and y_t needs to be types that can convert respectively to a double
and a bool (because the skeleton uses:
if (cutfilename()) htemp->Fill(macrofilename());
These two functions are run in a context such that the branch names are
available as local variables of the correct (read-only) type.
Note that if you use the same 'variable' twice, it is more efficient
to 'cache' the value. For example
Int_t n = fEventNumber; // Read fEventNumber
if (n<10 || n>10) { ... }
is more efficient than
if (fEventNumber<10 || fEventNumber>10)
Also, optionally, the generated selector will also call methods named
macrofilename_methodname in each of 6 main selector methods if the method
macrofilename_methodname exist (Where macrofilename is stripped of its
extension).
Concretely, with the script named h1analysisProxy.C,
The method calls the method (if it exist)
Begin -> h1analysisProxy_Begin
SlaveBegin -> h1analysisProxy_SlaveBegin
Notify -> h1analysisProxy_Notify
Process -> h1analysisProxy_Process
SlaveTerminate -> h1analysisProxy_SlaveTerminate
Terminate -> h1analysisProxy_Terminate
If a file name macrofilename.h (or .hh, .hpp, .hxx, .hPP, .hXX) exist
it is included before the declaration of the proxy class. This can
be used in particular to insure that the include files needed by
the macro file are properly loaded.
The default histogram is accessible via the variable named 'htemp'.
If the library of the classes describing the data in the branch is
loaded, the skeleton will add the needed #include statements and
give the ability to access the object stored in the branches.
To draw px using the file hsimple.root (generated by the
hsimple.C tutorial), we need a file named hsimple.cxx:
double hsimple() {
return px;
}
MakeProxy can then be used indirectly via the TTree::Draw interface
as follow:
new TFile("hsimple.root")
ntuple->Draw("hsimple.cxx");
A more complete example is available in the tutorials directory:
h1analysisProxy.cxx , h1analysProxy.h and h1analysisProxyCut.C
which reimplement the selector found in h1analysis.C
Int_t MakeSelector(const char* selector)
-- Generate skeleton selector class for this tree.
The following files are produced: selector.h and selector.C.
If selector is 0, the selector will be called "nameoftree".
The generated code in selector.h includes the following:
- Identification of the original Tree and Input file name
- Definition of selector class (data and functions)
- The following class functions:
- constructor and destructor
- void Begin(TTree *tree)
- void Init(TTree *tree)
- Bool_t Notify()
- Bool_t Process(Long64_t entry)
- void Terminate
The class selector derives from TSelector.
The generated code in selector.C includes empty functions defined above:
To use this function:
- connect your Tree file (eg: TFile f("myfile.root");)
- T->MakeSelector("myselect");
where T is the name of the Tree in file myfile.root
and myselect.h, myselect.C the name of the files created by this function.
In a ROOT session, you can do:
root > T->Process("select.C")
TTree* MergeTrees(TList* li, Option_t* )
-- Static function merging the trees in the TList into a new tree.
Trees in the list can be memory or disk-resident trees.
The new tree is created in the current directory (memory if gROOT).
Bool_t Notify()
-- Function called when loading a new class library.
TPrincipal* Principal(const char* varexp, const char* selection, Option_t* option, Long64_t nentries, Long64_t firstentry)
-- Interface to the Principal Components Analysis class.
Create an instance of TPrincipal
Fill it with the selected variables
if option "n" is specified, the TPrincipal object is filled with
normalized variables.
If option "p" is specified, compute the principal components
If option "p" and "d" print results of analysis
If option "p" and "h" generate standard histograms
If option "p" and "c" generate code of conversion functions
return a pointer to the TPrincipal object. It is the user responsability
to delete this object.
The option default value is "np"
see TTree::Draw for explanation of the other parameters.
The created object is named "principal" and a reference to it
is added to the list of specials Root objects.
you can retrieve a pointer to the created object via:
TPrincipal *principal =
(TPrincipal*)gROOT->GetListOfSpecials()->FindObject("principal");
void Print(Option_t* option)
-- Print a summary of the tree contents.
If option contains "all" friend trees are also printed.
If option contains "toponly" only the top level branches are printed.
Wildcarding can be used to print only a subset of the branches, e.g.,
T.Print("Elec*") will print all branches with name starting with "Elec".
Long64_t Process(const char* filename, Option_t* option, Long64_t nentries, Long64_t firstentry)
Process this tree executing the code in filename.
The return value is -1 in case of error and TSelector::GetStatus() in
in case of success.
The code in filename is loaded (interpreted or compiled , see below)
filename must contain a valid class implementation derived from TSelector.
where TSelector has the following member functions:
void TSelector::Begin(). This function is called before looping on the
events in the Tree. The user can create his histograms in this function.
Bool_t TSelector::ProcessCut(Long64_t entry). This function is called
before processing entry. It is the user's responsability to read
the corresponding entry in memory (may be just a partial read).
The function returns kTRUE if the entry must be processed,
kFALSE otherwise.
void TSelector::ProcessFill(Long64_t entry). This function is called for
all selected events. User fills histograms in this function.
void TSelector::Terminate(). This function is called at the end of
the loop on all events.
void TTreeProcess::Begin(). This function is called before looping on the
events in the Tree. The user can create his histograms in this function.
if filename is of the form file.C, the file will be interpreted.
if filename is of the form file.C++, the file file.C will be compiled
and dynamically loaded.
if filename is of the form file.C+, the file file.C will be compiled
and dynamically loaded. At next call, if file.C is older than file.o
and file.so, the file.C is not compiled, only file.so is loaded.
The function returns the number of processed entries. It returns -1
in case of an error.
NOTE1
It may be more interesting to invoke directly the other Process function
accepting a TSelector* as argument.eg
MySelector *selector = (MySelector*)TSelector::GetSelector(filename);
selector->CallSomeFunction(..);
mytree.Process(selector,..);
NOTE2
One should not call this function twice with the same selector file
in the same script. If this is required, proceed as indicated in NOTE1,
by getting a pointer to the corresponding TSelector,eg
workaround 1
------------
void stubs1() {
TSelector *selector = TSelector::GetSelector("h1test.C");
TFile *f1 = new TFile("stubs_nood_le1.root");
TTree *h1 = (TTree*)f1->Get("h1");
h1->Process(selector);
TFile *f2 = new TFile("stubs_nood_le1_coarse.root");
TTree *h2 = (TTree*)f2->Get("h1");
h2->Process(selector);
}
or use ACLIC to compile the selector
workaround 2
------------
void stubs2() {
TFile *f1 = new TFile("stubs_nood_le1.root");
TTree *h1 = (TTree*)f1->Get("h1");
h1->Process("h1test.C+");
TFile *f2 = new TFile("stubs_nood_le1_coarse.root");
TTree *h2 = (TTree*)f2->Get("h1");
h2->Process("h1test.C+");
}
Long64_t Process(TSelector* selector, Option_t* option, Long64_t nentries, Long64_t firstentry)
Process this tree executing the code in selector.
The return value is -1 in case of error and TSelector::GetStatus() in
in case of success.
The TSelector class has the following member functions:
void TSelector::Begin(). This function is called before looping on the
events in the Tree. The user can create his histograms in this function.
Bool_t TSelector::ProcessCut(Long64_t entry). This function is called
before processing entry. It is the user's responsability to read
the corresponding entry in memory (may be just a partial read).
The function returns kTRUE if the entry must be processed,
kFALSE otherwise.
void TSelector::ProcessFill(Long64_t entry). This function is called for
all selected events. User fills histograms in this function.
void TSelector::Terminate(). This function is called at the end of
the loop on all events.
void TTreeProcess::Begin(). This function is called before looping on the
events in the Tree. The user can create his histograms in this function.
Long64_t Project(const char* hname, const char* varexp, const char* selection, Option_t* option, Long64_t nentries, Long64_t firstentry)
-- Make a projection of a tree using selections.
Depending on the value of varexp (described in Draw) a 1-D, 2-D, etc.,
projection of the tree will be filled in histogram hname.
Note that the dimension of hname must match with the dimension of varexp.
Long64_t ReadFile(const char* filename, const char* branchDescriptor)
-- Create or simply read branches from filename.
if branchDescriptor = "" (default), it is assumed that the Tree descriptor
is given in the first line of the file with a syntax like
A/D:Table[2]/F:Ntracks/I:astring/C
otherwise branchDescriptor must be specified with the above syntax.
Lines in the input file starting with "#" are ignored.
A TBranch object is created for each variable in the expression.
The total number of rows read from the file is returned.
void Refresh()
-- Refresh contents of this tree and its branches from the current status on disk.
One can call this function in case the tree file is being
updated by another process.
void Reset(Option_t* option)
-- Reset baskets, buffers and entries count in all branches and leaves.
void ResetBranchAddresses()
-- Tell all of our branches to drop their current objects and allocate new ones.
Long64_t Scan(const char* varexp, const char* selection, Option_t* option, Long64_t nentries, Long64_t firstentry)
-- Loop over tree entries and print entries passing selection.
If varexp is 0 (or "") then print only first 8 columns.
If varexp = "*" print all columns.
Otherwise a columns selection can be made using "var1:var2:var3".
See TTreePlayer::Scan for more information
Bool_t SetAlias(const char* aliasName, const char* aliasFormula)
-- Set a tree variable alias.
Set an alias for an expression/formula based on the tree 'variables'.
The content of 'aliasName' can be used in TTreeFormula (i.e. TTree::Draw,
TTree::Scan, TTreeViewer) and will be evaluated as the content of
'aliasFormula'.
If the content of 'aliasFormula' only contains symbol names, periods and
array index specification (for example event.fTracks[3]), then
the content of 'aliasName' can be used as the start of symbol.
If the alias 'aliasName' already existed, it is replaced by the new
value.
When being used, the alias can be preceded by an eventual 'Friend Alias'
(see TTree::GetFriendAlias)
Return true if it was added properly.
For example:
tree->SetAlias("x1","(tdc1[1]-tdc1[0])/49");
tree->SetAlias("y1","(tdc1[3]-tdc1[2])/47");
tree->SetAlias("x2","(tdc2[1]-tdc2[0])/49");
tree->SetAlias("y2","(tdc2[3]-tdc2[2])/47");
tree->Draw("y2-y1:x2-x1");
tree->SetAlias("theGoodTrack","event.fTracks[3]");
tree->Draw("theGoodTrack.fPx"); // same as "event.fTracks[3].fPx"
void SetBasketSize(const char* bname, Int_t buffsize)
-- Set a branch's basket size.
bname is the name of a branch.
if bname="*", apply to all branches.
if bname="xxx*", apply to all branches with name starting with xxx
see TRegexp for wildcarding options
buffsize = branc basket size
void SetBranchAddress(const char* bname, void* addr, TBranch** ptr)
-- Change branch address, dealing with clone trees properly.
void SetBranchStatus(const char* bname, Bool_t status, UInt_t* found)
-- Set branch status to Process or DoNotProcess.
When reading a Tree, by default, all branches are read.
One can speed up considerably the analysis phase by activating
only the branches that hold variables involved in a query.
bname is the name of a branch.
if bname="*", apply to all branches.
if bname="xxx*", apply to all branches with name starting with xxx
see TRegexp for wildcarding options
status = 1 branch will be processed
= 0 branch will not be processed
Example:
Assume a tree T with sub-branches a,b,c,d,e,f,g,etc..
when doing T.GetEntry(i) all branches are read for entry i.
to read only the branches c and e, one can do
T.SetBranchStatus("*",0); //disable all branches
T.SetBranchStatus("c",1);
T.setBranchStatus("e",1);
T.GetEntry(i);
WARNING! WARNING! WARNING!
SetBranchStatus is matching the branch based on regular expression match
of the branch 'name' and not on the branch hierarchy!
In order to be able to selectively enable a top level object that is 'split'
you need to make sure the name of the top level branch is prefixed to the
sub-branches' name(by adding a dot ('.') at the end of the Branch creation
and use the corresponding regular expression.
I.e If your Tree has been created in split mode with a parent branch "parent."
(note the trailing dot).
T.SetBranchStatus("parent",1);
will not activate the sub-branches of "parent". You should do:
T.SetBranchStatus("parent*",1);
Without the trailing dot in the branch creation you have no choice but to
call SetBranchStatus explicitly for each of the sub branches.
An alternative to this function is to read directly and only
the interesting branches. Example:
TBranch *brc = T.GetBranch("c");
TBranch *bre = T.GetBranch("e");
brc->GetEntry(i);
bre->GetEntry(i);
If found is not 0, the number of branch(es) found matching the regular
expression is returned in *found AND the error message 'unknown branch'
is suppressed.
void SetCacheSize(Long64_t cacheSize)
-- Set maximum size of the file cache (default is 10000000, i.e., 10 MB).
if cachesize <= 0 the existing cache (if any) is deleted
void SetCircular(Long64_t maxEntries)
-- Enable/Disable circularity for this tree.
if maxEntries > 0 a maximum of maxEntries is kept in one buffer/basket
per branch in memory.
Note that when this function is called (maxEntries>0) the Tree
must be empty or having only one basket per branch.
if maxEntries <= 0 the tree circularity is disabled.
NOTE 1:
Circular Trees are interesting in online real time environments
to store the results of the last maxEntries events.
NOTE 2:
Calling SetCircular with maxEntries <= 0 is necessary before
merging circular Trees that have been saved on files.
NOTE 3:
SetCircular with maxEntries <= 0 is automatically called
by TChain::Merge
NOTE 4:
A circular Tree can still be saved in a file. When read back,
it is still a circular Tree and can be filled again.
void SetDirectory(TDirectory* dir)
-- Change the tree's directory.
Remove reference to this tree from current directory and
add reference to new directory dir. The dir parameter can
be 0 in which case the tree does not belong to any directory.
Long64_t SetEntries(Long64_t n)
-- Change number of entries in the tree.
If n >= 0, set number of entries in the tree = n.
If n < 0, set number of entries in the tree to match the
number of entries in each branch. (default for n is -1)
This function should be called only when one fills each branch
independently via TBranch::Fill without calling TTree::Fill.
Calling TTree::SetEntries() make sense only if the number of entries
in each branch is identical, a warning is issued otherwise.
The function returns the number of entries.
void SetMaxTreeSize(Long64_t maxsize)
-- Set the maximum size of a Tree file -- (static function).
In TTree::Fill, when the file has a size > fgMaxTreeSize,
the function closes the current file and starts writing into
a new file with a name of the style "file_1.root" if the original
requested file name was "file.root".
void SetName(const char* name)
-- Change the name of this tree.
void SetObject(const char* name, const char* title)
-- Change the name and title of this tree.
void SetWeight(Double_t w, Option_t*)
-- Set tree weight.
The weight is used by TTree::Draw to automatically weight each
selected entry in the resulting histogram.
For example the equivalent of:
T.Draw("x", "w")
is:
T.SetWeight(w);
T.Draw("x");
This function is redefined by TChain::SetWeight. In case of a
TChain, an option "global" may be specified to set the same weight
for all trees in the TChain instead of the default behaviour
using the weights of each tree in the chain (see TChain::SetWeight).
void Show(Long64_t entry, Int_t lenmax)
-- Print values of all active leaves for entry.
if entry==-1, print current entry (default)
if a leaf is an array, a maximum of lenmax elements is printed.
void StartViewer()
-- Start the TTreeViewer on this tree.
ww is the width of the canvas in pixels
wh is the height of the canvas in pixels
Long64_t UnbinnedFit(const char* funcname, const char* varexp, const char* selection, Option_t* option, Long64_t nentries, Long64_t firstentry)
-- Unbinned fit of one or more variable(s) from a tree.
funcname is a TF1 function.
See TTree::Draw for explanations of the other parameters.
Fit the variable varexp using the function funcname using the
selection cuts given by selection.
The list of fit options is given in parameter option.
option = "Q" Quiet mode (minimum printing)
= "V" Verbose mode (default is between Q and V)
= "E" Perform better Errors estimation using Minos technique
= "M" More. Improve fit results
You can specify boundary limits for some or all parameters via
func->SetParLimits(p_number, parmin, parmax);
if parmin>=parmax, the parameter is fixed
Note that you are not forced to fix the limits for all parameters.
For example, if you fit a function with 6 parameters, you can do:
func->SetParameters(0,3.1,1.e-6,0.1,-8,100);
func->SetParLimits(4,-10,-4);
func->SetParLimits(5, 1,1);
With this setup, parameters 0->3 can vary freely
Parameter 4 has boundaries [-10,-4] with initial value -8
Parameter 5 is fixed to 100.
For the fit to be meaningful, the function must be self-normalized.
i.e. It must have the same integral regardless of the parameter
settings. Otherwise the fit will effectively just maximize the
area.
It is mandatory to have a normalization variable
which is fixed for the fit. e.g.
TF1* f1 = new TF1("f1", "gaus(0)/sqrt(2*3.14159)/[2]", 0, 5);
f1->SetParameters(1, 3.1, 0.01);
f1->SetParLimits(0, 1, 1); // fix the normalization parameter to 1
data->UnbinnedFit("f1", "jpsimass", "jpsipt>3.0");
1, 2 and 3 Dimensional fits are supported.
See also TTree::Fit
Author: Rene Brun 12/01/96
Last update: root/tree:$Name: $:$Id: TTree.cxx,v 1.311 2006/11/25 00:15:26 pcanal Exp $
Copyright (C) 1995-2000, Rene Brun and Fons Rademakers. *
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