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Reference Guide
drawsparse.C File Reference

Detailed Description

View in nbviewer Open in SWAN Convert a THnSparse to a TTree using efficient iteration through the THnSparse and draw a THnSparse using TParallelCoord.

The plot will contain one line for each filled bin, with the bin's coordinates on each axis, and the bin's content on the rightmost axis.

Run as

.L $ROOTSYS/tutorials/tree/drawsparse.C+
Definition: tree.py:1
#include "TParallelCoord.h"
#include "TROOT.h"
#include "TTree.h"
#include "TLeaf.h"
#include "THnSparse.h"
#include "TAxis.h"
#include "TCanvas.h"
#include "TRandom.h"
#include "TFile.h"
#include "TH3.h"
TTree* toTree(THnSparse* h)
// Creates a TTree and fills it with the coordinates of all
// filled bins. The tree will have one branch for each dimension,
// and one for the bin content.
Int_t dim = h->GetNdimensions();
TString name(h->GetName()); name += "_tree";
TString title(h->GetTitle()); title += " tree";
TTree* tree = new TTree(name, title);
Double_t* x = new Double_t[dim + 1];
memset(x, 0, sizeof(Double_t) * (dim + 1));
TString branchname;
for (Int_t d = 0; d < dim; ++d) {
if (branchname.Length())
branchname += ":";
TAxis* axis = h->GetAxis(d);
branchname += axis->GetName();
branchname += "/D";
tree->Branch("coord", x, branchname);
tree->Branch("bincontent", &x[dim], "bincontent/D");
Int_t *bins = new Int_t[dim];
for (Long64_t i = 0; i < h->GetNbins(); ++i) {
x[dim] = h->GetBinContent(i, bins);
for (Int_t d = 0; d < dim; ++d) {
x[d] = h->GetAxis(d)->GetBinCenter(bins[d]);
delete [] bins;
//delete [] x;
return tree;
void drawsparse_draw(THnSparse* h)
// Draw a THnSparse using TParallelCoord, creating a temporary TTree.
TTree* tree = toTree(h);
TString whatToDraw;
TIter iLeaf(tree->GetListOfLeaves());
const TLeaf* leaf = 0;
while ((leaf = (const TLeaf*)iLeaf())) {
if (whatToDraw.Length())
whatToDraw += ":";
whatToDraw += leaf->GetName();
tree->Draw(whatToDraw, "", "para");
TParallelCoord* parallelCoord = (TParallelCoord*)gPad->GetListOfPrimitives()->FindObject("ParaCoord");
TIter iVar(parallelCoord->GetVarList());
for (Int_t d = 0;(var = (TParallelCoordVar*) iVar()) && d < h->GetNdimensions(); ++d) {
TAxis* axis = h->GetAxis(d);
var->SetCurrentLimits(axis->GetXmin(), axis->GetXmax());
var->SetTitle("bin content");
void drawsparse()
// create a THnSparse and draw it.
const Int_t ndims = 8;
Int_t bins[ndims] = {10, 10, 5, 30, 10, 4, 18, 12};
Double_t xmin[ndims] = {-5., -10., -1000., -3., 0., 0., 0., 0.};
Double_t xmax[ndims] = {10., 70., 3000., 3., 5., 2., 2., 5.};
THnSparse* hs = new THnSparseD("hs", "Sparse Histogram", ndims, bins, xmin, xmax);
// fill it
Double_t x[ndims];
for (Long_t i = 0; i < 100000; ++i) {
for (Int_t d = 0; d < ndims; ++d) {
switch (d) {
case 0: x[d] = gRandom->Gaus()*2 + 3.; break;
case 1:
case 2:
case 3: x[d] = (x[d-1]*x[d-1] - 1.5)/1.5 + (0.5*gRandom->Rndm()); break;
default: x[d] = sin(gRandom->Gaus()*i/1000.) + 1.;
TFile* f = new TFile("drawsparse.root","RECREATE");
TCanvas* canv = new TCanvas("hDrawSparse", "Drawing a sparse hist");
// draw it
// project it
TH3D* h3proj = hs->Projection(2, 3, 6);
// save everything to a file
delete f;
#define d(i)
Definition: RSha256.hxx:102
#define f(i)
Definition: RSha256.hxx:104
#define h(i)
Definition: RSha256.hxx:106
int Int_t
Definition: RtypesCore.h:45
long Long_t
Definition: RtypesCore.h:54
double Double_t
Definition: RtypesCore.h:59
long long Long64_t
Definition: RtypesCore.h:73
@ kOrange
Definition: Rtypes.h:67
char name[80]
Definition: TGX11.cxx:110
float xmin
Definition: THbookFile.cxx:95
float xmax
Definition: THbookFile.cxx:95
THnSparseT< TArrayD > THnSparseD
Definition: THnSparse.h:219
double sin(double)
R__EXTERN TRandom * gRandom
Definition: TRandom.h:62
#define gPad
Definition: TVirtualPad.h:287
virtual void SetLineColor(Color_t lcolor)
Set the line color.
Definition: TAttLine.h:40
Class to manage histogram axis.
Definition: TAxis.h:30
Double_t GetXmax() const
Definition: TAxis.h:134
Double_t GetXmin() const
Definition: TAxis.h:133
Int_t GetNbins() const
Definition: TAxis.h:121
const char * GetTitle() const
Returns title of object.
Definition: TAxis.h:129
The Canvas class.
Definition: TCanvas.h:23
TVirtualPad * cd(Int_t subpadnumber=0) override
Set current canvas & pad.
Definition: TCanvas.cxx:708
A ROOT file is a suite of consecutive data records (TKey instances) with a well defined format.
Definition: TFile.h:54
virtual void SetDirectory(TDirectory *dir)
By default when an histogram is created, it is added to the list of histogram objects in the current ...
Definition: TH1.cxx:8777
virtual void Draw(Option_t *option="")
Draw this histogram with options.
Definition: TH1.cxx:3073
3-D histogram with a double per channel (see TH1 documentation)}
Definition: TH3.h:305
Long64_t Fill(const Double_t *x, Double_t w=1.)
Definition: THnBase.h:144
Efficient multidimensional histogram.
Definition: THnSparse.h:36
TH1D * Projection(Int_t xDim, Option_t *option="") const
Forwards to THnBase::Projection().
Definition: THnSparse.h:133
A TLeaf describes individual elements of a TBranch See TBranch structure in TTree.
Definition: TLeaf.h:57
virtual const char * GetName() const
Returns name of object.
Definition: TNamed.h:47
virtual Int_t Write(const char *name=0, Int_t option=0, Int_t bufsize=0)
Write this object to the current directory.
Definition: TObject.cxx:798
void Divide(Int_t nx=1, Int_t ny=1, Float_t xmargin=0.01, Float_t ymargin=0.01, Int_t color=0) override
Automatic pad generation by division.
Definition: TPad.cxx:1177
TParallelCoord axes.
void SetTitle(const char *)
Set the title of the TNamed.
void SetHistogramBinning(Int_t n=100)
Set the histogram binning.
void SetCurrentLimits(Double_t min, Double_t max)
Set the limits within which one the entries must be painted.
Parallel Coordinates class.
TList * GetVarList()
virtual Double_t Gaus(Double_t mean=0, Double_t sigma=1)
Samples a random number from the standard Normal (Gaussian) Distribution with the given mean and sigm...
Definition: TRandom.cxx:274
virtual Double_t Rndm()
Machine independent random number generator.
Definition: TRandom.cxx:552
Basic string class.
Definition: TString.h:136
Ssiz_t Length() const
Definition: TString.h:410
A TTree represents a columnar dataset.
Definition: TTree.h:79
Double_t x[n]
Definition: legend1.C:17
Axel Naumann

Definition in file drawsparse.C.