A class to chain together multiple histograms.

This class allows to chain together any THnBase-derived (THn or THnSparse) histograms from multiple files. Operations on the axes and projections are supported. The intent is to allow convenient merging merging of projections of high-dimensional histograms.

// `file1.root` and `file2.root` contain a `THnSparse` named `hsparse`.
THnChain hs("hsparse");
hs.AddFile("file1.root");
hs.AddFile("file2.root");
 
// Project out axis 0, integrate over other axes.
TH1* h0 = hs.Projection(0);
 
// Project out axis 0, integrate over other axes in their active ranges.
hs.GetAxis(1)->SetRangeUser(0, 0.1); // select a subrange
TH1* h0 = hs.Projection(0);

Definition at line 49 of file THnChain.h.

Public Member Functions
	THnChain (const char *name)
	Default constructor.

void	AddFile (const char *fileName)
	Add a new file to this chain.

TAxis *	GetAxis (Int_t i) const
	Get an axis from the histogram.

TClass *	IsA () const override

TH3 *	Projection (Int_t xDim, Int_t yDim, Int_t zDim, Option_t *option="") const
	See `THnBase::Projection` for the intended behavior.

TH1 *	Projection (Int_t xDim, Option_t *option="") const
	See `THnBase::Projection` for the intended behavior.

TH2 *	Projection (Int_t yDim, Int_t xDim, Option_t *option="") const
	See `THnBase::Projection` for the intended behavior.

THnBase *	ProjectionND (Int_t ndim, const Int_t dim, Option_t option="") const
	See `THnBase::Projection` for the intended behavior.

void	Streamer (TBuffer &) override
	Stream an object of class TObject.

void	StreamerNVirtual (TBuffer &ClassDef_StreamerNVirtual_b)

Public Member Functions inherited from TObject
	TObject ()
	TObject constructor.

	TObject (const TObject &object)
	TObject copy ctor.

virtual	~TObject ()
	TObject destructor.

void	AbstractMethod (const char *method) const
	Use this method to implement an "abstract" method that you don't want to leave purely abstract.

virtual void	AppendPad (Option_t *option="")
	Append graphics object to current pad.

virtual void	Browse (TBrowser *b)
	Browse object. May be overridden for another default action.

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.

virtual const char *	ClassName () const
	Returns name of class to which the object belongs.

virtual void	Clear (Option_t *="")

virtual TObject *	Clone (const char *newname="") const
	Make a clone of an object using the Streamer facility.

virtual Int_t	Compare (const TObject *obj) const
	Compare abstract method.

virtual void	Copy (TObject &object) const
	Copy this to obj.

virtual void	Delete (Option_t *option="")
	Delete this object.

virtual Int_t	DistancetoPrimitive (Int_t px, Int_t py)
	Computes distance from point (px,py) to the object.

virtual void	Draw (Option_t *option="")
	Default Draw method for all objects.

virtual void	DrawClass () const
	Draw class inheritance tree of the class to which this object belongs.

virtual TObject *	DrawClone (Option_t *option="") const
	Draw a clone of this object in the current selected pad with: `gROOT->SetSelectedPad(c1)`.

virtual void	Dump () const
	Dump contents of object on stdout.

virtual void	Error (const char method, const char msgfmt,...) const
	Issue error message.

virtual void	Execute (const char method, const char params, Int_t *error=nullptr)
	Execute method on this object with the given parameter string, e.g.

virtual void	Execute (TMethod method, TObjArray params, Int_t *error=nullptr)
	Execute method on this object with parameters stored in the TObjArray.

virtual void	ExecuteEvent (Int_t event, Int_t px, Int_t py)
	Execute action corresponding to an event at (px,py).

virtual void	Fatal (const char method, const char msgfmt,...) const
	Issue fatal error message.

virtual TObject *	FindObject (const char *name) const
	Must be redefined in derived classes.

virtual TObject *	FindObject (const TObject *obj) const
	Must be redefined in derived classes.

virtual Option_t *	GetDrawOption () const
	Get option used by the graphics system to draw this object.

virtual const char *	GetIconName () const
	Returns mime type name of object.

virtual const char *	GetName () const
	Returns name of object.

virtual char *	GetObjectInfo (Int_t px, Int_t py) const
	Returns string containing info about the object at position (px,py).

virtual Option_t *	GetOption () const

virtual const char *	GetTitle () const
	Returns title of object.

virtual UInt_t	GetUniqueID () const
	Return the unique object id.

virtual Bool_t	HandleTimer (TTimer *timer)
	Execute action in response of a timer timing out.

virtual ULong_t	Hash () const
	Return hash value for this object.

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.

virtual void	Info (const char method, const char msgfmt,...) const
	Issue info message.

virtual Bool_t	InheritsFrom (const char *classname) const
	Returns kTRUE if object inherits from class "classname".

virtual Bool_t	InheritsFrom (const TClass *cl) const
	Returns kTRUE if object inherits from TClass cl.

virtual void	Inspect () const
	Dump contents of this object in a graphics canvas.

void	InvertBit (UInt_t f)

Bool_t	IsDestructed () const
	IsDestructed.

virtual Bool_t	IsEqual (const TObject *obj) const
	Default equal comparison (objects are equal if they have the same address in memory).

virtual Bool_t	IsFolder () const
	Returns kTRUE in case object contains browsable objects (like containers or lists of other objects).

R__ALWAYS_INLINE Bool_t	IsOnHeap () const

virtual Bool_t	IsSortable () const

R__ALWAYS_INLINE Bool_t	IsZombie () const

virtual void	ls (Option_t *option="") const
	The ls function lists the contents of a class on stdout.

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).

virtual Bool_t	Notify ()
	This method must be overridden to handle object notification (the base implementation is no-op).

void	Obsolete (const char method, const char asOfVers, const char *removedFromVers) const
	Use this method to declare a method obsolete.

void	operator delete (void *ptr)
	Operator delete.

void	operator delete (void ptr, void vp)
	Only called by placement new when throwing an exception.

void	operator delete[] (void *ptr)
	Operator delete [].

void	operator delete[] (void ptr, void vp)
	Only called by placement new[] when throwing an exception.

void *	operator new (size_t sz)

void *	operator new (size_t sz, void *vp)

void *	operator new[] (size_t sz)

void *	operator new[] (size_t sz, void *vp)

TObject &	operator= (const TObject &rhs)
	TObject assignment operator.

virtual void	Paint (Option_t *option="")
	This method must be overridden if a class wants to paint itself.

virtual void	Pop ()
	Pop on object drawn in a pad to the top of the display list.

virtual void	Print (Option_t *option="") const
	This method must be overridden when a class wants to print itself.

virtual Int_t	Read (const char *name)
	Read contents of object with specified name from the current directory.

virtual void	RecursiveRemove (TObject *obj)
	Recursively remove this object from a list.

void	ResetBit (UInt_t f)

virtual void	SaveAs (const char filename="", Option_t option="") const
	Save this object in the file specified by filename.

virtual void	SavePrimitive (std::ostream &out, Option_t *option="")
	Save a primitive as a C++ statement(s) on output stream "out".

void	SetBit (UInt_t f)

void	SetBit (UInt_t f, Bool_t set)
	Set or unset the user status bits as specified in f.

virtual void	SetDrawOption (Option_t *option="")
	Set drawing option for object.

virtual void	SetUniqueID (UInt_t uid)
	Set the unique object id.

void	StreamerNVirtual (TBuffer &ClassDef_StreamerNVirtual_b)

virtual void	SysError (const char method, const char msgfmt,...) const
	Issue system error message.

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.

virtual void	Warning (const char method, const char msgfmt,...) const
	Issue warning message.

virtual Int_t	Write (const char *name=nullptr, Int_t option=0, Int_t bufsize=0)
	Write this object to the current directory.

virtual Int_t	Write (const char *name=nullptr, Int_t option=0, Int_t bufsize=0) const
	Write this object to the current directory.

Static Public Member Functions
static TClass *	Class ()

static const char *	Class_Name ()

static constexpr Version_t	Class_Version ()

static const char *	DeclFileName ()

Static Public Member Functions inherited from TObject
static TClass *	Class ()

static const char *	Class_Name ()

static constexpr Version_t	Class_Version ()

static const char *	DeclFileName ()

static Longptr_t	GetDtorOnly ()
	Return destructor only flag.

static Bool_t	GetObjectStat ()
	Get status of object stat flag.

static void	SetDtorOnly (void *obj)
	Set destructor only flag.

static void	SetObjectStat (Bool_t stat)
	Turn on/off tracking of objects in the TObjectTable.

Private Member Functions
TObject *	ProjectionAny (Int_t ndim, const Int_t dim, Option_t option="") const
	Projects all histograms in the chain.

THnBase *	ReadHistogram (const char *fileName) const
	Retrieve a histogram from a file.

void	SetupAxes (THnBase &hs) const
	Copy the properties of all axes to a histogram.

Static Private Member Functions
static bool	CheckConsistency (const THnBase &h, const std::vector< TAxis * > &axes)
	Ensure a histogram has axes similar to the ones we expect.

Private Attributes
std::vector< TAxis * >	fAxes
	the list of histogram axes

std::vector< std::string >	fFiles
	a list of files to extract the histogram from

std::string	fName
	name of the histogram

Additional Inherited Members
Public Types inherited from TObject
enum	{ kIsOnHeap = 0x01000000 , kNotDeleted = 0x02000000 , kZombie = 0x04000000 , kInconsistent = 0x08000000 , kBitMask = 0x00ffffff }

enum	{ kSingleKey = (1ULL << ( 0 )) , kOverwrite = (1ULL << ( 1 )) , kWriteDelete = (1ULL << ( 2 )) }

enum	EDeprecatedStatusBits { kObjInCanvas = (1ULL << ( 3 )) }

enum	EStatusBits { kCanDelete = (1ULL << ( 0 )) , kMustCleanup = (1ULL << ( 3 )) , kIsReferenced = (1ULL << ( 4 )) , kHasUUID = (1ULL << ( 5 )) , kCannotPick = (1ULL << ( 6 )) , kNoContextMenu = (1ULL << ( 8 )) , kInvalidObject = (1ULL << ( 13 )) }

Protected Types inherited from TObject
enum	{ kOnlyPrepStep = (1ULL << ( 3 )) }

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).

void	MakeZombie ()

#include <THnChain.h>

Inheritance diagram for THnChain:

[legend]

Constructor & Destructor Documentation

◆ THnChain()

THnChain::THnChain ( const char * name )

inlineexplicit

Default constructor.

Parameters

name	name of the histogram to work on

Definition at line 55 of file THnChain.h.

Member Function Documentation

◆ AddFile()

void THnChain::AddFile ( const char * fileName )

Add a new file to this chain.

Parameters

fileName path of the file to add

Definition at line 27 of file THnChain.cxx.

◆ CheckConsistency()

bool THnChain::CheckConsistency	(	const THnBase &	h,
		const std::vector< TAxis * > &	axes
	)

staticprivate

Ensure a histogram has axes similar to the ones we expect.

Parameters

h	histogram to verify
axes	expected set of axes

Definition at line 171 of file THnChain.cxx.

◆ Class()

static TClass * THnChain::Class ( )

static

Returns: TClass describing this class

◆ Class_Name()

static const char * THnChain::Class_Name ( )

static

Returns: Name of this class

◆ Class_Version()

static constexpr Version_t THnChain::Class_Version ( )

inlinestaticconstexpr

Returns: Version of this class

Definition at line 83 of file THnChain.h.

◆ DeclFileName()

static const char * THnChain::DeclFileName ( )

inlinestatic

Returns: Name of the file containing the class declaration

Definition at line 83 of file THnChain.h.

◆ GetAxis()

TAxis * THnChain::GetAxis ( Int_t i ) const

Get an axis from the histogram.

Parameters

i	index of the axis to retrieve

This function requires that a file containing the histogram was already added with AddFile.

Properties set on the axis returned by GetAxis are propagated to all histograms in the chain, so it can e.g. be used to set ranges for projections.

Definition at line 59 of file THnChain.cxx.

◆ IsA()

TClass * THnChain::IsA ( ) const

inlineoverridevirtual

Returns: TClass describing current object

Reimplemented from TObject.

Definition at line 83 of file THnChain.h.

◆ Projection() [1/3]

TH3 * THnChain::Projection	(	Int_t	xDim,
		Int_t	yDim,
		Int_t	zDim,
		Option_t *	option = `""`
	)		const

See THnBase::Projection for the intended behavior.

Definition at line 238 of file THnChain.cxx.

◆ Projection() [2/3]

TH1 * THnChain::Projection	(	Int_t	xDim,
		Option_t *	option = `""`
	)		const

See THnBase::Projection for the intended behavior.

Definition at line 222 of file THnChain.cxx.

◆ Projection() [3/3]

TH2 * THnChain::Projection	(	Int_t	yDim,
		Int_t	xDim,
		Option_t *	option = `""`
	)		const

See THnBase::Projection for the intended behavior.

Definition at line 230 of file THnChain.cxx.

◆ ProjectionAny()

TObject * THnChain::ProjectionAny	(	Int_t	ndim,
		const Int_t *	dim,
		Option_t *	option = `""`
	)		const

private

Projects all histograms in the chain.

See THnBase::Projection for parameters and their semantics.

Definition at line 71 of file THnChain.cxx.

◆ ProjectionND()

THnBase * THnChain::ProjectionND	(	Int_t	ndim,
		const Int_t *	dim,
		Option_t *	option = `""`
	)		const

See THnBase::Projection for the intended behavior.

Definition at line 246 of file THnChain.cxx.

◆ ReadHistogram()

THnBase * THnChain::ReadHistogram ( const char * fileName ) const

private

Retrieve a histogram from a file.

Parameters

fileName path of the file to read.

Definition at line 137 of file THnChain.cxx.

◆ SetupAxes()

void THnChain::SetupAxes ( THnBase & hs ) const

private

Copy the properties of all axes to a histogram.

Parameters

hs	histogram whose axes should be updated

Definition at line 157 of file THnChain.cxx.

◆ Streamer()

void THnChain::Streamer ( TBuffer & R__b )

overridevirtual

Stream an object of class TObject.

Reimplemented from TObject.

◆ StreamerNVirtual()

void THnChain::StreamerNVirtual ( TBuffer & ClassDef_StreamerNVirtual_b )

inline

Definition at line 83 of file THnChain.h.

Member Data Documentation

◆ fAxes

std::vector<TAxis*> THnChain::fAxes

private

the list of histogram axes

Definition at line 73 of file THnChain.h.

◆ fFiles

std::vector<std::string> THnChain::fFiles

private

a list of files to extract the histogram from

Definition at line 72 of file THnChain.h.

◆ fName

std::string THnChain::fName

private

name of the histogram

Definition at line 70 of file THnChain.h.

Libraries for THnChain:

[legend]

The documentation for this class was generated from the following files:

hist/hist/inc/THnChain.h
hist/hist/src/THnChain.cxx

Public Member Functions

Static Public Member Functions

Private Member Functions

Static Private Member Functions

Private Attributes

Additional Inherited Members

Constructor & Destructor Documentation

◆ THnChain()

Member Function Documentation

◆ AddFile()

◆ CheckConsistency()

◆ Class()

◆ Class_Name()

◆ Class_Version()

◆ DeclFileName()

◆ GetAxis()

◆ IsA()

◆ Projection() [1/3]

◆ Projection() [2/3]

◆ Projection() [3/3]

◆ ProjectionAny()

◆ ProjectionND()

◆ ReadHistogram()

◆ SetupAxes()

◆ Streamer()

◆ StreamerNVirtual()

Member Data Documentation

◆ fAxes

◆ fFiles

◆ fName