- Set Sumw2 for all histos in the histo container

[u/mrichter/AliRoot.git] / PWGJE / EMCALJetTasks / UserTasks / AliEMCalHistoContainer.cxx

/**************************************************************************
 * Copyright(c) 1998-2007, ALICE Experiment at CERN, All rights reserved. *
 *                                                                        *
 * Author: The ALICE Off-line Project.                                    *
 * Contributors are mentioned in the code where appropriate.              *
 *                                                                        *
 * Permission to use, copy, modify and distribute this software and its   *
 * documentation strictly for non-commercial purposes is hereby granted   *
 * without fee, provided that the above copyright notice appears in all   *
 * copies and that both the copyright notice and this permission notice   *
 * appear in the supporting documentation. The authors make no claims     *
 * about the suitability of this software for any purpose. It is          *
 * provided "as is" without express or implied warranty.                  *
 **************************************************************************/

/*
 * Container class for histogram objects. Currenly can handle
 *   TH1
 *   TH2
 *   TH3
 *   THnSparse
 * Histograms can be stored in groups. For this the parent group is 
 * included inside the histogram name, i.e. /base/inheriting/histogram.
 * In case just the histogram name is given, it is assumed that the
 * histogram is stored at the top level.
 *
 *   Author: Markus Fasel
 */

#include <cstring>
#include <vector>
#include <TArrayD.h>
#include <TAxis.h>
#include <TH1.h>
#include <TH2.h>
#include <TH3.h>
#include <THnSparse.h>
#include <THashList.h>
#include <TObjArray.h>
#include <TObjString.h>
#include <TString.h>

#include "AliLog.h"

#include "AliEMCalHistoContainer.h"

ClassImp(EMCalTriggerPtAnalysis::AliEMCalHistoContainer)

namespace EMCalTriggerPtAnalysis {

  //______________________________________________________________________________
  AliEMCalHistoContainer::AliEMCalHistoContainer():
                		        TNamed(),
                		        fHistos(NULL),
                		        fIsOwner(true)
  {
    /*
     * Default constructor, only initialising pointers with 0
     */
  }

  //______________________________________________________________________________
  AliEMCalHistoContainer::AliEMCalHistoContainer(const char *name):
                		        TNamed(name, Form("Histogram container %s", name)),
                		        fHistos(NULL),
                		        fIsOwner(true)
  {
    /*
     * Main constructor, creating also a list for the histograms
     *
     * @param name: Name of the object (list named accordingly)
     */
    fHistos = new THashList();
    fHistos->SetName(Form("histos%s", name));
    fHistos->SetOwner();
  }

  //______________________________________________________________________________
  AliEMCalHistoContainer::~AliEMCalHistoContainer(){
    /*
     * Destructor, deletes the list of histograms if it is the owner
     */
    if(fHistos && fIsOwner) delete fHistos;
  }

  //______________________________________________________________________________
  void AliEMCalHistoContainer::CreateHistoGroup(const char *groupname, const char *parent) throw(HistoContainerContentException) {
    /*
     * Create a new group of histograms within a parent group. Groups are represented as list. The default parent is
     * always the top list. List name structure accouding to unix paths (i.e. top list /, hirarchies separated by /).
     *
     * @param groupname: Name of the new group
     * @param parent (@default "/"): Name of the parent group
     * @throw HistoContainerContentException
     */
    THashList *parentgroup = FindGroup(parent);
    if(!parentgroup) throw HistoContainerContentException(NULL, parent, HistoContainerContentException::kGroupException);
    THashList *childgroup = new THashList();
    childgroup->SetName(groupname);
    parentgroup->Add(childgroup);
  }

  //______________________________________________________________________________
  void AliEMCalHistoContainer::CreateTH1(const char *name, const char *title, int nbins, double xmin, double xmax) throw(HistoContainerContentException){
    /*
     * Create a new TH1 within the container. The histogram name also contains the parent group(s) according to the common
     * group notation.
     *
     * @param name: Name of the histogram
     * @param title: Title of the histogram
     * @param nbins: number of bins
     * @param xmin: min. value of the range
     * @param xmax: max. value of the range
     * @throw HistoContainerContentException
     */
    TString dirname(basename(name)), hname(histname(name));
    THashList *parent(FindGroup(dirname.Data()));
    if(!parent)
      throw HistoContainerContentException(NULL, dirname.Data(), HistoContainerContentException::kGroupException);
    if(parent->FindObject(hname.Data()))
      throw HistoContainerContentException(hname.Data(), dirname.Data(), HistoContainerContentException::kHistDuplicationException);
    TH1 *hist = new TH1D(hname.Data(), title, nbins, xmin, xmax);
    hist->Sumw2();
    parent->Add(hist);
  }

  //______________________________________________________________________________
  void AliEMCalHistoContainer::CreateTH1(const char *name, const char *title, int nbins, const double *xbins) throw(HistoContainerContentException){
    /*
     * Create a new TH1 within the container. The histogram name also contains the parent group(s) according to the common
     * group notation.
     *
     * @param name: Name of the histogram
     * @param title: Title of the histogram
     * @param nbins: number of bins
     * @param xbins: array of bin limits
     * @throw HistoContainerContentException
     */
    TString dirname(basename(name)), hname(histname(name));
    THashList *parent(FindGroup(dirname));
    if(!parent)
      throw HistoContainerContentException(NULL, dirname.Data(), HistoContainerContentException::kGroupException);
    if(parent->FindObject(hname.Data()))
      throw HistoContainerContentException(hname, dirname.Data(), HistoContainerContentException::kHistDuplicationException);
    TH1 *hist = new TH1D(hname.Data(), title, nbins, xbins);
    hist->Sumw2();
    parent->Add(hist);
  }

  //______________________________________________________________________________
  void AliEMCalHistoContainer::CreateTH1(const char *name, const char *title, const TArrayD &xbins) throw(HistoContainerContentException){
    /*
     * Create a new TH1 within the container. The histogram name also contains the parent group(s) according to the common
     * group notation.
     *
     * @param name: Name of the histogram
     * @param title: Title of the histogram
     * @param xbins: array of bin limits (contains also number of bins)
     * @throw HistoContainerContentException
     */
    TString dirname(basename(name)), hname(histname(name));
    THashList *parent(FindGroup(dirname));
    if(!parent)
      throw HistoContainerContentException(NULL, dirname.Data(), HistoContainerContentException::kGroupException);
    if(parent->FindObject(hname.Data()))
      throw HistoContainerContentException(hname.Data(), dirname.Data(), HistoContainerContentException::kHistDuplicationException);
    TH1 *hist = new TH1D(hname.Data(), title, xbins.GetSize()-1, xbins.GetArray());
    hist->Sumw2();
    parent->Add(hist);
  }

  //______________________________________________________________________________
  void AliEMCalHistoContainer::CreateTH2(const char *name, const char *title,
      int nbinsx, double xmin, double xmax, int nbinsy, double ymin, double ymax) throw(HistoContainerContentException){
    /*
     * Create a new TH2 within the container. The histogram name also contains the parent group(s) according to the common
     * group notation.
     *
     * @param name: Name of the histogram
     * @param title: Title of the histogram
     * @param nbinsx: number of bins in x-direction
     * @param xmin: min. value of the range in x-direction
     * @param xmax: max. value of the range in x-direction
     * @param nbinsy: number of bins in y-direction
     * @param ymin: min. value of the range in y-direction
     * @param ymax: max. value of the range in y-direction
     * @throw HistoContainerContentException
     */
    TString dirname(basename(name)), hname(histname(name));
    THashList *parent(FindGroup(dirname.Data()));
    if(!parent)
      throw HistoContainerContentException(NULL, dirname.Data(), HistoContainerContentException::kGroupException);
    if(parent->FindObject(hname.Data()))
      throw HistoContainerContentException(hname.Data(), dirname.Data(), HistoContainerContentException::kHistDuplicationException);
    TH2 *hist = new TH2D(hname.Data(), title, nbinsx, xmin, xmax, nbinsy, ymin, ymax);
    parent->Add(hist);
  }

  //______________________________________________________________________________
  void AliEMCalHistoContainer::CreateTH2(const char *name, const char *title,
      int nbinsx, const double *xbins, int nbinsy, const double *ybins) throw(HistoContainerContentException){
    /*
     * Create a new TH2 within the container. The histogram name also contains the parent group(s) according to the common
     * group notation.
     *
     * @param name: Name of the histogram
     * @param title: Title of the histogram
     * @param nbinsx: number of bins in x-direction
     * @param xbins: array of bin limits in x-direction
     * @param nbinsy: number of bins in y-direction
     * @param ybins: array of bin limits in y-direction
     * @throw HistoContainerContentException
     */
    TString dirname(basename(name)), hname(histname(name));
    THashList *parent(FindGroup(dirname.Data()));
    if(!parent)
      throw HistoContainerContentException(NULL, dirname.Data(), HistoContainerContentException::kGroupException);
    if(parent->FindObject(hname.Data()))
      throw HistoContainerContentException(hname.Data(), dirname.Data(), HistoContainerContentException::kHistDuplicationException);
    TH2 *hist = new TH2D(hname.Data(), title, nbinsx, xbins, nbinsy, ybins);
    hist->Sumw2();
    parent->Add(hist);
  }

  //______________________________________________________________________________
  void AliEMCalHistoContainer::CreateTH2(const char *name, const char *title, const TArrayD &xbins, const TArrayD &ybins) throw(HistoContainerContentException){
    /*
     * Create a new TH2 within the container. The histogram name also contains the parent group(s) according to the common
     * group notation.
     *
     * @param name: Name of the histogram
     * @param title: Title of the histogram
     * @param xbins: array of bin limits in x-direction (contains also the number of bins)
     * @param ybins: array of bin limits in y-direction (contains also the number of bins)
     * @throw HistoContainerContentException
     */
    TString dirname(basename(name)), hname(histname(name));
    THashList *parent(FindGroup(dirname.Data()));
    if(!parent)
      throw HistoContainerContentException(NULL, dirname.Data(), HistoContainerContentException::kGroupException);
    if(parent->FindObject(hname.Data()))
      throw HistoContainerContentException(hname.Data(), dirname.Data(), HistoContainerContentException::kHistDuplicationException);
    TH2 *hist = new TH2D(hname.Data(), title, xbins.GetSize() - 1, xbins.GetArray(), ybins.GetSize() - 1, ybins.GetArray());
    hist->Sumw2();
    parent->Add(hist);
  }

  //______________________________________________________________________________
  void AliEMCalHistoContainer::CreateTH3(const char* name, const char* title, int nbinsx, double xmin, double xmax,
      int nbinsy, double ymin, double ymax, int nbinsz, double zmin, double zmax) throw (HistoContainerContentException) {
    /*
     * Create a new TH3 within the container. The histogram name also contains the parent group(s) according to the common
     * group notation.
     *
     * @param nbinsx: number of bins in x-direction
     * @param xmin: min. value of the range in x-direction
     * @param xmax: max. value of the range in x-direction
     * @param nbinsy: number of bins in y-direction
     * @param ymin: min. value of the range in y-direction
     * @param ymax: max. value of the range in y-direction
     * @param nbinsz: number of bins in z-direction
     * @param zmin: min. value of the range in z-direction
     * @param zmax: max. value of the range in z-direction
     * @throw HistoContainerContentException
     */
    TString dirname(basename(name)), hname(histname(name));
    THashList *parent(FindGroup(dirname.Data()));
    if(!parent)
      throw HistoContainerContentException(NULL, dirname.Data(), HistoContainerContentException::kGroupException);
    if(parent->FindObject(hname.Data()))
      throw HistoContainerContentException(hname.Data(), dirname.Data(), HistoContainerContentException::kHistDuplicationException);
    TH3 *hist = new TH3D(hname.Data(), title, nbinsx, xmin, xmax, nbinsy, ymin, ymax, nbinsz, zmin, zmax);
    hist->Sumw2();
    parent->Add(hist);
  }

  //______________________________________________________________________________
  void AliEMCalHistoContainer::CreateTH3(const char* name, const char* title, int nbinsx, const double* xbins,
      int nbinsy, const double* ybins, int nbinsz, const double* zbins) throw (HistoContainerContentException) {
    /*
     * Create a new TH3 within the container. The histogram name also contains the parent group(s) according to the common
     * group notation.
     *
     * @param name: Name of the histogram
     * @param title: Title of the histogram
     * @param nbinsx: number of bins in x-direction
     * @param xbins: array of bin limits in x-direction
     * @param nbinsy: number of bins in y-direction
     * @param ybins: array of bin limits in y-direction
     * @param nbinsz: number of bins in z-direction
     * @param zbins: array of bin limits in z-direction
     * @throw HistoContainerContentException
     */
    TString dirname(basename(name)), hname(histname(name));
    THashList *parent(FindGroup(dirname.Data()));
    if(!parent)
      throw HistoContainerContentException(NULL, dirname.Data(), HistoContainerContentException::kGroupException);
    if(parent->FindObject(hname.Data()))
      throw HistoContainerContentException(hname.Data(), dirname.Data(), HistoContainerContentException::kHistDuplicationException);
    TH3 *hist = new TH3D(hname.Data(), title, nbinsx, xbins, nbinsy, ybins, nbinsz, zbins);
    hist->Sumw2();
    parent->Add(hist);
  }

  //______________________________________________________________________________
  void AliEMCalHistoContainer::CreateTH3(const char* name, const char* title, const TArrayD& xbins, const TArrayD& ybins,
      const TArrayD& zbins) throw (HistoContainerContentException) {
    /*
     * Create a new TH3 within the container. The histogram name also contains the parent group(s) according to the common
     * group notation.
     *
     * @param name: Name of the histogram
     * @param title: Title of the histogram
     * @param xbins: array of bin limits in x-direction (contains also the number of bins)
     * @param ybins: array of bin limits in y-direction (contains also the number of bins)
     * @param zbins: array of bin limits in z-direction (contains also the number of bins)
     * @throw HistoContainerContentException
     */
    TString dirname(basename(name)), hname(histname(name));
    THashList *parent(FindGroup(dirname.Data()));
    if(!parent)
      throw HistoContainerContentException(NULL, dirname.Data(), HistoContainerContentException::kGroupException);
    if(parent->FindObject(hname.Data()))
      throw HistoContainerContentException(hname.Data(), dirname.Data(), HistoContainerContentException::kHistDuplicationException);
    TH3 *hist = new TH3D(hname.Data(), title, xbins.GetSize()-1, xbins.GetArray(), ybins.GetSize()-1, ybins.GetArray(), zbins.GetSize()-1, zbins.GetArray());
    hist->Sumw2();
    parent->Add(hist);
  }

  //______________________________________________________________________________
  void AliEMCalHistoContainer::CreateTHnSparse(const char *name, const char *title,
      int ndim, const int *nbins, const double *min, const double *max) throw(HistoContainerContentException){
    /*
     * Create a new THnSparse within the container. The histogram name also contains the parent group(s) according to the common
     * group notation.
     *
     * @param name: Name of the histogram
     * @param title: Title of the histogram
     * @param ndim: Number of dimensions
     * @param nbins: Number of bins per dimension
     * @param min: min. value of the range for each dimension
     * @param max: max. value of the range for each dimension
     * @throw HistoContainerContentException
     */
    TString dirname(basename(name)), hname(histname(name));
    THashList *parent(FindGroup(dirname.Data()));
    if(!parent)
      throw HistoContainerContentException(NULL, dirname.Data(), HistoContainerContentException::kGroupException);
    if(parent->FindObject(hname.Data()))
      throw HistoContainerContentException(hname.Data(), dirname.Data(), HistoContainerContentException::kHistDuplicationException);
    THnSparseD *hist = new THnSparseD(hname.Data(), title, ndim, nbins, min, max);
    hist->Sumw2();
    parent->Add(hist);
  }

  //______________________________________________________________________________
  void AliEMCalHistoContainer::CreateTHnSparse(const char *name, const char *title, int ndim, const TAxis **axes) throw(HistoContainerContentException){
    /*
     * Create a new THnSparse within the container. The histogram name also contains the parent group(s) according to the common
     * group notation.
     *
     * @param name: Name of the histogram
     * @param title: Title of the histogram
     * @param ndim: Number of dimensions
     * @param axes: Array of pointers to TAxis for containing the axis definition for each dimension
     * @throw HistoContainerContentException
     */
    TString dirname(basename(name)), hname(histname(name));
    THashList *parent(FindGroup(dirname.Data()));
    if(!parent)
      throw HistoContainerContentException(NULL, dirname.Data(), HistoContainerContentException::kGroupException);
    if(parent->FindObject(hname))
      throw HistoContainerContentException(hname.Data(), dirname.Data(), HistoContainerContentException::kHistDuplicationException);
    TArrayD xmin(ndim), xmax(ndim);
    TArrayI nbins(ndim);
    for(int idim = 0; idim < ndim; ++idim){
      const TAxis &myaxis = *(axes[idim]);
      nbins[idim] = myaxis.GetNbins();
      xmin[idim] = myaxis.GetXmin();
      xmax[idim] = myaxis.GetXmax();
    }
    THnSparseD *hsparse = new THnSparseD(hname.Data(), title, ndim, nbins.GetArray(), xmin.GetArray(), xmax.GetArray());
    for(int id = 0; id < ndim; ++id)
      *(hsparse->GetAxis(id)) = *(axes[id]);
    hsparse->Sumw2();
    parent->Add(hsparse);
  }

  //______________________________________________________________________________
  void AliEMCalHistoContainer::SetObject(TObject * const o, const char *group) throw(HistoContainerContentException){
    /*
     * Set a new group into the container into the parent group
     *
     * @param o: the object ot be included

     */
    THashList *parent(FindGroup(group));
    if(!parent)
      throw HistoContainerContentException(NULL, strcmp(group, "/") ? group : "", HistoContainerContentException::kGroupException);
    if(parent->FindObject(o->GetName()))
      throw HistoContainerContentException(o->GetName(), strcmp(group, "/") ? group : "", HistoContainerContentException::kHistDuplicationException);
    if(!(dynamic_cast<THnBase *>(o) || dynamic_cast<TH1 *>(o)))
      throw HistoContainerContentException(o->GetName(), strcmp(group, "/") ? group : "", HistoContainerContentException::kTypeException);
    fHistos->Add(o);
  }

  //______________________________________________________________________________
  void AliEMCalHistoContainer::FillTH1(const char *name, double x, double weight) throw(HistoContainerContentException){
    /*
     * Fill a 1D histogram within the container. The histogram name also contains the parent group(s) according to the common
     * group notation.
     *
     * @param name: Name of the histogram
     * @param x: x-coordinate
     * @param weight (@default 1): optional weight of the entry
     * @throw HistoContainerContentException
     */
    TString dirname(basename(name)), hname(histname(name));
    THashList *parent(FindGroup(dirname.Data()));
    if(!parent)
      throw HistoContainerContentException(NULL, dirname.Data(), HistoContainerContentException::kGroupException);
    TH1 *hist = dynamic_cast<TH1 *>(parent->FindObject(hname.Data()));
    if(!hist)
      throw HistoContainerContentException(hname.Data(), dirname.Data(), HistoContainerContentException::kHistNotFoundException);
    hist->Fill(x, weight);
  }

  //______________________________________________________________________________
  void AliEMCalHistoContainer::FillTH2(const char *name, double x, double y, double weight) throw(HistoContainerContentException){
    /*
     * Fill a 2D histogram within the container. The histogram name also contains the parent group(s) according to the common
     * group notation.
     *
     * @param name: Name of the histogram
     * @param x: x-coordinate
     * @param y: y-coordinate
     * @param weight (@default 1): optional weight of the entry
     * @throw HistoContainerContentException
     */
    TString dirname(basename(name)), hname(histname(name));
    THashList *parent(FindGroup(dirname.Data()));
    if(!parent)
      throw HistoContainerContentException(NULL, dirname.Data(), HistoContainerContentException::kGroupException);
    TH2 *hist = dynamic_cast<TH2 *>(parent->FindObject(hname.Data()));
    if(!hist)
      throw HistoContainerContentException(hname.Data(), dirname.Data(), HistoContainerContentException::kHistNotFoundException);
    hist->Fill(x, y, weight);
  }

  //______________________________________________________________________________
  void AliEMCalHistoContainer::FillTH2(const char *name, double *point, double weight) throw(HistoContainerContentException){
    /*
     * Fill a 2D histogram within the container. The histogram name also contains the parent group(s) according to the common
     * group notation.
     *
     * @param name: Name of the histogram
     * @param point: coordinates of the data
     * @param weight (@default 1): optional weight of the entry
     * @throw HistoContainerContentException
     */
    TString dirname(basename(name)), hname(histname(name));
    THashList *parent(FindGroup(dirname.Data()));
    if(!parent)
      throw HistoContainerContentException(NULL, dirname.Data(), HistoContainerContentException::kGroupException);
    TH2 *hist = dynamic_cast<TH2 *>(parent->FindObject(hname.Data()));
    if(!hist)
      throw HistoContainerContentException(hname.Data(), dirname.Data(), HistoContainerContentException::kHistNotFoundException);
    hist->Fill(point[0], point[1], weight);
  }

  //______________________________________________________________________________
  void AliEMCalHistoContainer::FillTH3(const char* name, double x, double y, double z, double weight) throw (HistoContainerContentException) {
    /*
     * Fill a 3D histogram within the container. The histogram name also contains the parent group(s) according to the common
     * group notation.
     *
     * @param name: Name of the histogram
     * @param x: x-coordinate
     * @param y: y-coordinate
     * @param z: z-coordinate
     * @param weight (@default 1): optional weight of the entry
     * @throw HistoContainerContentException
     */
    TString dirname(basename(name)), hname(histname(name));
    THashList *parent(FindGroup(dirname.Data()));
    if(!parent)
      throw HistoContainerContentException(NULL, dirname.Data(), HistoContainerContentException::kGroupException);
    TH3 *hist = dynamic_cast<TH3 *>(parent->FindObject(hname.Data()));
    if(!hist)
      throw HistoContainerContentException(hname.Data(), dirname.Data(), HistoContainerContentException::kHistNotFoundException);
    hist->Fill(x, y, z, weight);
  }

  //______________________________________________________________________________
  void AliEMCalHistoContainer::FillTH3(const char* name, const double* point, double weight) throw (HistoContainerContentException) {
    TString dirname(basename(name)), hname(histname(name));
    THashList *parent(FindGroup(dirname.Data()));
    if(!parent)
      throw HistoContainerContentException(NULL, dirname.Data(), HistoContainerContentException::kGroupException);
    TH3 *hist = dynamic_cast<TH3 *>(parent->FindObject(hname.Data()));
    if(!hist)
      throw HistoContainerContentException(hname.Data(), dirname.Data(), HistoContainerContentException::kHistNotFoundException);
    hist->Fill(point[0], point[1], point[2], weight);
  }


  //______________________________________________________________________________
  void AliEMCalHistoContainer::FillTHnSparse(const char *name, const double *x, double weight) throw(HistoContainerContentException){
    /*
     * Fill a  nD histogram within the container. The histogram name also contains the parent group(s) according to the common
     * group notation.
     *
     * @param name: Name of the histogram
     * @param x: coordinates of the data
     * @param weight (@default 1): optional weight of the entry
     * @throw HistoContainerContentException
     */
    TString dirname(basename(name)), hname(histname(name));
    THashList *parent(FindGroup(dirname.Data()));
    if(!parent)
      throw HistoContainerContentException(NULL, dirname.Data(), HistoContainerContentException::kGroupException);
    THnSparseD *hist = dynamic_cast<THnSparseD *>(parent->FindObject(hname.Data()));
    if(!hist)
      throw HistoContainerContentException(hname.Data(), dirname.Data(), HistoContainerContentException::kHistNotFoundException);
    hist->Fill(x, weight);
  }

  //______________________________________________________________________________
  TObject *AliEMCalHistoContainer::FindObject(const char *name) const {
    /*
     * Find an object inside the container. The object can also be within a
     * histogram group. For this the name has to follow the common notation
     *
     * @param name: Name of the object to find inside the container
     * @return: pointer to the object (NULL if not found)
     */
    TString dirname(basename(name)), hname(histname(name));
    THashList *parent(FindGroup(dirname.Data()));
    if(!parent) return NULL;
    return parent->FindObject(hname);
  }

  //______________________________________________________________________________
  TObject* AliEMCalHistoContainer::FindObject(const TObject* obj) const {
    /*
     * Find and object inside the container. The object name is expected to contain the
     * full path of the histogram object, including parent groups
     *
     * @param obj: the object to find
     * @return: pointer to the object (NULL if not found)
     */
    TString dirname(basename(obj->GetName())), hname(histname(obj->GetName()));
    THashList *parent(FindGroup(dirname.Data()));
    if(!parent) return NULL;
    return parent->FindObject(hname);
  }

  //______________________________________________________________________________
  THashList *AliEMCalHistoContainer::FindGroup(const char *dirname) const {
    /*
     * Find histogram group. Name is using common notation
     *
     * @param dirname: Path of the group (treat empty path as top node
     * @return: TList of objects (NULL if group does not exist)
     */
    if(!strlen(dirname) || !strcmp(dirname, "/")) return fHistos;
    std::vector<std::string> tokens;
    TokenizeFilename(dirname, "/", tokens);
    THashList *currentdir(fHistos);
    for(std::vector<std::string>::iterator it = tokens.begin(); it != tokens.end(); ++it){
      currentdir = dynamic_cast<THashList *>(currentdir->FindObject(it->c_str()));
      if(!currentdir) break;
    }
    return currentdir;
  }

  //______________________________________________________________________________
  void AliEMCalHistoContainer::TokenizeFilename(const char *name, const char *delim, std::vector<std::string> &listoftokens) const {
    /*
     * Tokenizes a string. Results are stored inside the vector listoftokens
     *
     * @ param name: string to be tokenised
     * @ param delim: delimiter string
     * @ param listoftokens: list of tokens (C++ strings)
     */
    TString s(name);
    TObjArray *arr = s.Tokenize(delim);
    TObjString *ostr(NULL);
    TIter toks(arr);
    while((ostr = dynamic_cast<TObjString *>(toks()))){
      listoftokens.push_back(std::string(ostr->String().Data()));
    }
    delete arr;
  }

  //______________________________________________________________________________
  const char *AliEMCalHistoContainer::basename(const char *path) const {
    /*
     * Helper function extracting the basename from a given histogram path.
     *
     * @param path: histogram path
     * @return: basename extracted
     */
    TString s(path);
    int index = s.Last('/');
    if(index < 0) return "";  // no directory structure
    return TString(s(0, index)).Data();
  }

  //______________________________________________________________________________
  const char *AliEMCalHistoContainer::histname(const char *path) const {
    /*
     * Helper function extracting the histogram name from a given histogram path.
     *
     * @param path: histogram path
     * @return: basename extracted
     */
    TString s(path);
    int index = s.Last('/');
    if(index < 0) return path;    // no directory structure
    return TString(s(index+1, s.Length() - (index+1))).Data();
  }
}