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Reference Guide
RooStats::SPlot Class Reference

A class to calculate "sWeights" used to create an "sPlot". An sPlot can reweight a dataset to show different components (e.g. signal / background), but it doesn't use cuts, and therefore doesn't have to sort events into signal/background (or other) categories. Instead of assigning a category to each event in the dataset, all events are weighted. To compute the weights, a PDF with different components is analysed, and the weights are added to the dataset. When plotting the dataset with the weights of the signal or background components, the data looks like "signal", but all events in the dataset are used.

The result is similar to a likelihood projection plot, but without cuts.

Note
SPlot needs to fit the pdf to the data once, so make sure that all relevant fit arguments such as the fit range are passed in the constructor.

The code is based on `‘SPlot: A statistical tool to unfold data distributions,’' Nucl. Instrum. Meth. A 555, 356 (2005) [arXiv:physics/0402083].

Creating an SPlot

To use this class, you first must have a pdf that includes yield parameters for (possibly several) different species, for example a signal and background yield. Those yields must be of type RooRealVar / RooLinearVar (or anything that derives from RooAbsRealLValue). This is necessary because RooStats needs to be able to set the yields to 0 and 1 to probe the PDF. After constructing the s weights, the yields will be restored to their original values.

To create an instance of the SPlot, supply a data set, the pdf to analyse, and a list which parameters of the pdf are yields. The SPlot will calculate SWeights, and include these as columns in the RooDataSet. The dataset will have two additional columns for every yield with name "`<varname>`":

  • L_<varname> is the the likelihood for each event, i.e., the pdf evaluated for the given value of the variable "varname".
  • <varname>_sw is the value of the sWeight for the variable "varname" for each event.

In SPlot::SPlot(), one can choose whether columns should be added to an existing dataset or whether a copy of the dataset should be created.

Plotting s-weighted data

After computing the s weights, create a new dataset that uses the s weights of the variable of interest for weighting. If the yield parameter for signal was e.g. "signalYield", the dataset can be constructed as follows:

RooDataSet data_signal("<name>", "<title>", <dataWithSWeights>, <variables>, 0, "signalYield_sw");

A complete tutorial with an extensive model is rs301_splot.C

Using ratios as yield parameters

As mentioned, RooStats needs to be able to modify the yield parameters. That means that they have to be a RooRealVar of a RooLinearVar. This allows using ratio parameters as in the following example:

RooRealVar x("x", "observable", 0, 0, 20);
RooRealVar m("m", "mean", 5., -10, 10);
RooRealVar s("s", "sigma", 2., 0, 10);
RooGaussian gaus("gaus", "gaus", x, m, s);
RooRealVar a("a", "exp", -0.2, -10., 0.);
RooExponential ex("ex", "ex", x, a);
RooRealVar common("common", "common scale", 3., 0, 10);
RooRealVar r1("r1", "ratio of signal events", 0.3, 0, 10);
RooRealVar r2("r2", "ratio of background events", 0.5, 0, 10);
RooLinearVar c1("c1", "c1", r1, common, RooFit::RooConst(0.));
RooLinearVar c2("c2", "c2", r2, common, RooFit::RooConst(0.));
RooAddPdf sum("sum", "sum", RooArgSet(gaus, ex), RooArgSet(c1, c2));
auto data = sum.generate(x, 1000);
RooStats::SPlot splot("splot", "splot", *data, &sum, RooArgSet(c1, c2));

Definition at line 32 of file SPlot.h.

Public Member Functions

 SPlot ()
 Default constructor. More...
 
 SPlot (const char *name, const char *title)
 
 SPlot (const char *name, const char *title, const RooDataSet &data)
 Constructor from a RooDataSet No sWeighted variables are present. More...
 
 SPlot (const char *name, const char *title, RooDataSet &data, RooAbsPdf *pdf, const RooArgList &yieldsList, const RooArgSet &projDeps=RooArgSet(), bool useWeights=kTRUE, bool copyDataSet=kFALSE, const char *newName="", const RooCmdArg &fitToarg5=RooCmdArg::none(), const RooCmdArg &fitToarg6=RooCmdArg::none(), const RooCmdArg &fitToarg7=RooCmdArg::none(), const RooCmdArg &fitToarg8=RooCmdArg::none())
 Construct a new SPlot instance, calculate sWeights, and include them in the RooDataSet held by this instance. More...
 
 SPlot (const SPlot &other)
 Copy Constructor from another SPlot. More...
 
 ~SPlot ()
 
void AddSWeight (RooAbsPdf *pdf, const RooArgList &yieldsTmp, const RooArgSet &projDeps=RooArgSet(), bool includeWeights=kTRUE, const RooCmdArg &fitToarg5=RooCmdArg::none(), const RooCmdArg &fitToarg6=RooCmdArg::none(), const RooCmdArg &fitToarg7=RooCmdArg::none(), const RooCmdArg &fitToarg8=RooCmdArg::none())
 Method which adds the sWeights to the dataset. More...
 
Int_t GetNumSWeightVars () const
 Return the number of SWeights In other words, return the number of species that we are trying to extract. More...
 
RooDataSetGetSDataSet () const
 Retrieve s-weighted data. More...
 
Double_t GetSumOfEventSWeight (Int_t numEvent) const
 Sum the SWeights for a particular event. More...
 
Double_t GetSWeight (Int_t numEvent, const char *sVariable) const
 Retrieve an s weight. More...
 
RooArgList GetSWeightVars () const
 Return a RooArgList containing all paramters that have s weights. More...
 
Double_t GetYieldFromSWeight (const char *sVariable) const
 Sum the SWeights for a particular species over all events. More...
 
RooDataSetSetSData (RooDataSet *data)
 Set dataset (if not passed in constructor). More...
 
- Public Member Functions inherited from TNamed
 TNamed ()
 
 TNamed (const char *name, const char *title)
 
 TNamed (const TNamed &named)
 TNamed copy ctor. More...
 
 TNamed (const TString &name, const TString &title)
 
virtual ~TNamed ()
 TNamed destructor. More...
 
virtual void Clear (Option_t *option="")
 Set name and title to empty strings (""). More...
 
virtual TObjectClone (const char *newname="") const
 Make a clone of an object using the Streamer facility. More...
 
virtual Int_t Compare (const TObject *obj) const
 Compare two TNamed objects. More...
 
virtual void Copy (TObject &named) const
 Copy this to obj. More...
 
virtual void FillBuffer (char *&buffer)
 Encode TNamed into output buffer. More...
 
virtual const char * GetName () const
 Returns name of object. More...
 
virtual const char * GetTitle () const
 Returns title of object. More...
 
virtual ULong_t Hash () const
 Return hash value for this object. More...
 
virtual Bool_t IsSortable () const
 
virtual void ls (Option_t *option="") const
 List TNamed name and title. More...
 
TNamedoperator= (const TNamed &rhs)
 TNamed assignment operator. More...
 
virtual void Print (Option_t *option="") const
 Print TNamed name and title. More...
 
virtual void SetName (const char *name)
 Set the name of the TNamed. More...
 
virtual void SetNameTitle (const char *name, const char *title)
 Set all the TNamed parameters (name and title). More...
 
virtual void SetTitle (const char *title="")
 Set the title of the TNamed. More...
 
virtual Int_t Sizeof () const
 Return size of the TNamed part of the TObject. More...
 
- Public Member Functions inherited from TObject
 TObject ()
 TObject constructor. More...
 
 TObject (const TObject &object)
 TObject copy ctor. More...
 
virtual ~TObject ()
 TObject destructor. More...
 
void AbstractMethod (const char *method) const
 Use this method to implement an "abstract" method that you don't want to leave purely abstract. More...
 
virtual void AppendPad (Option_t *option="")
 Append graphics object to current pad. More...
 
virtual void Browse (TBrowser *b)
 Browse object. May be overridden for another default action. More...
 
ULong_t CheckedHash ()
 Check and record whether this class has a consistent Hash/RecursiveRemove setup (*) and then return the regular Hash value for this object. More...
 
virtual const char * ClassName () const
 Returns name of class to which the object belongs. More...
 
virtual void Delete (Option_t *option="")
 Delete this object. More...
 
virtual Int_t DistancetoPrimitive (Int_t px, Int_t py)
 Computes distance from point (px,py) to the object. More...
 
virtual void Draw (Option_t *option="")
 Default Draw method for all objects. More...
 
virtual void DrawClass () const
 Draw class inheritance tree of the class to which this object belongs. More...
 
virtual TObjectDrawClone (Option_t *option="") const
 Draw a clone of this object in the current selected pad for instance with: gROOT->SetSelectedPad(gPad). More...
 
virtual void Dump () const
 Dump contents of object on stdout. More...
 
virtual void Error (const char *method, const char *msgfmt,...) const
 Issue error message. More...
 
virtual void Execute (const char *method, const char *params, Int_t *error=0)
 Execute method on this object with the given parameter string, e.g. More...
 
virtual void Execute (TMethod *method, TObjArray *params, Int_t *error=0)
 Execute method on this object with parameters stored in the TObjArray. More...
 
virtual void ExecuteEvent (Int_t event, Int_t px, Int_t py)
 Execute action corresponding to an event at (px,py). More...
 
virtual void Fatal (const char *method, const char *msgfmt,...) const
 Issue fatal error message. More...
 
virtual TObjectFindObject (const char *name) const
 Must be redefined in derived classes. More...
 
virtual TObjectFindObject (const TObject *obj) const
 Must be redefined in derived classes. More...
 
virtual Option_tGetDrawOption () const
 Get option used by the graphics system to draw this object. More...
 
virtual const char * GetIconName () const
 Returns mime type name of object. More...
 
virtual char * GetObjectInfo (Int_t px, Int_t py) const
 Returns string containing info about the object at position (px,py). More...
 
virtual Option_tGetOption () const
 
virtual UInt_t GetUniqueID () const
 Return the unique object id. More...
 
virtual Bool_t HandleTimer (TTimer *timer)
 Execute action in response of a timer timing out. More...
 
Bool_t HasInconsistentHash () const
 Return true is the type of this object is known to have an inconsistent setup for Hash and RecursiveRemove (i.e. More...
 
virtual void Info (const char *method, const char *msgfmt,...) const
 Issue info message. More...
 
virtual Bool_t InheritsFrom (const char *classname) const
 Returns kTRUE if object inherits from class "classname". More...
 
virtual Bool_t InheritsFrom (const TClass *cl) const
 Returns kTRUE if object inherits from TClass cl. More...
 
virtual void Inspect () const
 Dump contents of this object in a graphics canvas. More...
 
void InvertBit (UInt_t f)
 
virtual Bool_t IsEqual (const TObject *obj) const
 Default equal comparison (objects are equal if they have the same address in memory). More...
 
virtual Bool_t IsFolder () const
 Returns kTRUE in case object contains browsable objects (like containers or lists of other objects). More...
 
R__ALWAYS_INLINE Bool_t IsOnHeap () const
 
R__ALWAYS_INLINE Bool_t IsZombie () const
 
void MayNotUse (const char *method) const
 Use this method to signal that a method (defined in a base class) may not be called in a derived class (in principle against good design since a child class should not provide less functionality than its parent, however, sometimes it is necessary). More...
 
virtual Bool_t Notify ()
 This method must be overridden to handle object notification. More...
 
void Obsolete (const char *method, const char *asOfVers, const char *removedFromVers) const
 Use this method to declare a method obsolete. More...
 
void operator delete (void *ptr)
 Operator delete. More...
 
void operator delete[] (void *ptr)
 Operator delete []. More...
 
voidoperator new (size_t sz)
 
voidoperator new (size_t sz, void *vp)
 
voidoperator new[] (size_t sz)
 
voidoperator new[] (size_t sz, void *vp)
 
TObjectoperator= (const TObject &rhs)
 TObject assignment operator. More...
 
virtual void Paint (Option_t *option="")
 This method must be overridden if a class wants to paint itself. More...
 
virtual void Pop ()
 Pop on object drawn in a pad to the top of the display list. More...
 
virtual Int_t Read (const char *name)
 Read contents of object with specified name from the current directory. More...
 
virtual void RecursiveRemove (TObject *obj)
 Recursively remove this object from a list. More...
 
void ResetBit (UInt_t f)
 
virtual void SaveAs (const char *filename="", Option_t *option="") const
 Save this object in the file specified by filename. More...
 
virtual void SavePrimitive (std::ostream &out, Option_t *option="")
 Save a primitive as a C++ statement(s) on output stream "out". More...
 
void SetBit (UInt_t f)
 
void SetBit (UInt_t f, Bool_t set)
 Set or unset the user status bits as specified in f. More...
 
virtual void SetDrawOption (Option_t *option="")
 Set drawing option for object. More...
 
virtual void SetUniqueID (UInt_t uid)
 Set the unique object id. More...
 
virtual void SysError (const char *method, const char *msgfmt,...) const
 Issue system error message. More...
 
R__ALWAYS_INLINE Bool_t TestBit (UInt_t f) const
 
Int_t TestBits (UInt_t f) const
 
virtual void UseCurrentStyle ()
 Set current style settings in this object This function is called when either TCanvas::UseCurrentStyle or TROOT::ForceStyle have been invoked. More...
 
virtual void Warning (const char *method, const char *msgfmt,...) const
 Issue warning message. More...
 
virtual Int_t Write (const char *name=0, Int_t option=0, Int_t bufsize=0)
 Write this object to the current directory. More...
 
virtual Int_t Write (const char *name=0, Int_t option=0, Int_t bufsize=0) const
 Write this object to the current directory. More...
 

Protected Types

enum  { kOwnData = BIT(20) }
 

Protected Attributes

RooDataSetfSData
 
RooArgList fSWeightVars
 
- Protected Attributes inherited from TNamed
TString fName
 
TString fTitle
 

Additional Inherited Members

- Public Types inherited from TObject
enum  {
  kIsOnHeap = 0x01000000, kNotDeleted = 0x02000000, kZombie = 0x04000000, kInconsistent = 0x08000000,
  kBitMask = 0x00ffffff
}
 
enum  { kSingleKey = BIT(0), kOverwrite = BIT(1), kWriteDelete = BIT(2) }
 
enum  EDeprecatedStatusBits { kObjInCanvas = BIT(3) }
 
enum  EStatusBits {
  kCanDelete = BIT(0), kMustCleanup = BIT(3), kIsReferenced = BIT(4), kHasUUID = BIT(5),
  kCannotPick = BIT(6), kNoContextMenu = BIT(8), kInvalidObject = BIT(13)
}
 
- Static Public Member Functions inherited from TObject
static Long_t GetDtorOnly ()
 Return destructor only flag. More...
 
static Bool_t GetObjectStat ()
 Get status of object stat flag. More...
 
static void SetDtorOnly (void *obj)
 Set destructor only flag. More...
 
static void SetObjectStat (Bool_t stat)
 Turn on/off tracking of objects in the TObjectTable. More...
 
- Protected Member Functions inherited from TObject
virtual void DoError (int level, const char *location, const char *fmt, va_list va) const
 Interface to ErrorHandler (protected). More...
 
void MakeZombie ()
 

#include <RooStats/SPlot.h>

Inheritance diagram for RooStats::SPlot:
[legend]

Member Enumeration Documentation

◆ anonymous enum

anonymous enum
protected
Enumerator
kOwnData 

Definition at line 74 of file SPlot.h.

Constructor & Destructor Documentation

◆ ~SPlot()

SPlot::~SPlot ( )

Definition at line 120 of file SPlot.cxx.

◆ SPlot() [1/5]

SPlot::SPlot ( )

Default constructor.

Definition at line 130 of file SPlot.cxx.

◆ SPlot() [2/5]

SPlot::SPlot ( const SPlot other)

Copy Constructor from another SPlot.

Definition at line 171 of file SPlot.cxx.

◆ SPlot() [3/5]

SPlot::SPlot ( const char *  name,
const char *  title 
)

Definition at line 143 of file SPlot.cxx.

◆ SPlot() [4/5]

SPlot::SPlot ( const char *  name,
const char *  title,
const RooDataSet data 
)

Constructor from a RooDataSet No sWeighted variables are present.

Definition at line 158 of file SPlot.cxx.

◆ SPlot() [5/5]

SPlot::SPlot ( const char *  name,
const char *  title,
RooDataSet data,
RooAbsPdf pdf,
const RooArgList yieldsList,
const RooArgSet projDeps = RooArgSet(),
bool  useWeights = kTRUE,
bool  cloneData = kFALSE,
const char *  newName = "",
const RooCmdArg arg5 = RooCmdArg::none(),
const RooCmdArg arg6 = RooCmdArg::none(),
const RooCmdArg arg7 = RooCmdArg::none(),
const RooCmdArg arg8 = RooCmdArg::none() 
)

Construct a new SPlot instance, calculate sWeights, and include them in the RooDataSet held by this instance.

The constructor automatically calls AddSWeight() to add s weights to the dataset. These can be retrieved later using GetSWeight() or GetSDataSet().

Parameters
[in]nameName of the instance.
[in]titleTitle of the instance.
[in]dataDataset to fit to.
[in]pdfPDF to compute s weights for.
[in]yieldsListList of parameters in pdf that are yields. These must be RooRealVar or RooLinearVar, since RooStats will need to modify their values.
[in]projDepsDon't normalise over these parameters when calculating the sWeights. Will be passed on to AddSWeight().
[in]useWeightsInclude weights of the input data in calculation of s weights.
[in]cloneDataMake a clone of the incoming data before adding weights.
[in]newNameNew name for the data.
[in]argXAdditional arguments for the fitting step in AddSWeight().

Definition at line 198 of file SPlot.cxx.

Member Function Documentation

◆ AddSWeight()

void SPlot::AddSWeight ( RooAbsPdf pdf,
const RooArgList yieldsTmp,
const RooArgSet projDeps = RooArgSet(),
bool  includeWeights = kTRUE,
const RooCmdArg arg5 = RooCmdArg::none(),
const RooCmdArg arg6 = RooCmdArg::none(),
const RooCmdArg arg7 = RooCmdArg::none(),
const RooCmdArg arg8 = RooCmdArg::none() 
)

Method which adds the sWeights to the dataset.

The SPlot will contain two new variables for each yield parameter:

  • L_<varname> is the the likelihood for each event, i.e., the pdf evaluated for the a given value of the variable "varname".
  • <varname>_sw is the value of the sWeight for the variable "varname" for each event.

Find Parameters in the PDF to be considered fixed when calculating the SWeights and be sure to NOT include the yields in that list.

After fixing non-yield parameters, this function will start a fit by calling

One can pass additional arguments to fitTo, such as RooFit::Range("fitrange"), as arg5, arg6, arg7, arg8.

Note
A RooFit::Range may be necessary to get expected results if you initially fit in a range and/or called pdf->fixCoefRange("fitrange") on pdf. Pass arg5, arg6, arg7, arg8 AT YOUR OWN RISK.
Parameters
[in]pdfPDF to fit to data to compute s weights.
[in]yieldsTmpYields to use to compute s weights.
[in]projDepsThese will not be normalized over when calculating the sWeights, and will be considered parameters, not observables.
[in]includeWeightsInclude weights of the input data in calculation of s weights.
[in]argXOptional additional arguments for the fitting step.

Definition at line 419 of file SPlot.cxx.

◆ GetNumSWeightVars()

Int_t SPlot::GetNumSWeightVars ( ) const

Return the number of SWeights In other words, return the number of species that we are trying to extract.

Definition at line 386 of file SPlot.cxx.

◆ GetSDataSet()

RooDataSet * SPlot::GetSDataSet ( ) const

Retrieve s-weighted data.

It does not automatically call AddSWeight(). This needs to be done manually.

Definition at line 242 of file SPlot.cxx.

◆ GetSumOfEventSWeight()

Double_t SPlot::GetSumOfEventSWeight ( Int_t  numEvent) const

Sum the SWeights for a particular event.

This sum should equal the total weight of that event. This method is intended to be used as a check.

Definition at line 300 of file SPlot.cxx.

◆ GetSWeight()

Double_t SPlot::GetSWeight ( Int_t  numEvent,
const char *  sVariable 
) const

Retrieve an s weight.

Parameters
[in]numEventEvent number to retrieve s weight for.
[in]sVariableThe yield parameter to retrieve the s weight for.

Definition at line 251 of file SPlot.cxx.

◆ GetSWeightVars()

RooArgList SPlot::GetSWeightVars ( ) const

Return a RooArgList containing all paramters that have s weights.

Definition at line 372 of file SPlot.cxx.

◆ GetYieldFromSWeight()

Double_t SPlot::GetYieldFromSWeight ( const char *  sVariable) const

Sum the SWeights for a particular species over all events.

This should equal the total (weighted) yield of that species. This method is intended as a check.

Definition at line 331 of file SPlot.cxx.

◆ SetSData()

RooDataSet * SPlot::SetSData ( RooDataSet data)

Set dataset (if not passed in constructor).

Definition at line 230 of file SPlot.cxx.

Member Data Documentation

◆ fSData

RooDataSet* RooStats::SPlot::fSData
protected

Definition at line 82 of file SPlot.h.

◆ fSWeightVars

RooArgList RooStats::SPlot::fSWeightVars
protected

Definition at line 78 of file SPlot.h.

Libraries for RooStats::SPlot:
[legend]

The documentation for this class was generated from the following files:
m
auto * m
Definition: textangle.C:8
ex
Double_t ex[n]
Definition: legend1.C:17
kTRUE
const Bool_t kTRUE
Definition: RtypesCore.h:91
RooAddPdf
Definition: RooAddPdf.h:32
RooFit::PrintLevel
RooCmdArg PrintLevel(Int_t code)
Definition: RooGlobalFunc.cxx:189
RooFit::PrintEvalErrors
RooCmdArg PrintEvalErrors(Int_t numErrors)
Definition: RooGlobalFunc.cxx:205
RooFit::SumW2Error
RooCmdArg SumW2Error(Bool_t flag)
Definition: RooGlobalFunc.cxx:207
TGeant4Unit::s
static constexpr double s
Definition: TGeant4SystemOfUnits.h:168
x
Double_t x[n]
Definition: legend1.C:17
RooGaussian
Definition: RooGaussian.h:25
RooLinearVar
Definition: RooLinearVar.h:30
RooStats::SPlot
Definition: SPlot.h:32
RooStats::SPlot::fSData
RooDataSet * fSData
Definition: SPlot.h:82
TMVA::variables
void variables(TString dataset, TString fin="TMVA.root", TString dirName="InputVariables_Id", TString title="TMVA Input Variables", Bool_t isRegression=kFALSE, Bool_t useTMVAStyle=kTRUE)
a
auto * a
Definition: textangle.C:12
sum
static long int sum(long int i)
Definition: Factory.cxx:2272
c2
return c2
Definition: legend2.C:14
RooDataSet
Definition: RooDataSet.h:33
RooRealVar
Definition: RooRealVar.h:35
RooExponential
Definition: RooExponential.h:25
RooArgSet
Definition: RooArgSet.h:28
c1
return c1
Definition: legend1.C:41
RooFit::Extended
RooCmdArg Extended(Bool_t flag=kTRUE)
Definition: RooGlobalFunc.cxx:155
RooFit::RooConst
RooConstVar & RooConst(Double_t val)
Definition: RooGlobalFunc.cxx:341