TH1K.cxx

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// @(#)root/hist:$Id$
// Author: Victor Perevoztchikov <perev@bnl.gov>  21/02/2001
 
/*************************************************************************
 * Copyright (C) 1995-2000, Rene Brun and Fons Rademakers.               *
 * All rights reserved.                                                  *
 *                                                                       *
 * For the licensing terms see $ROOTSYS/LICENSE.                         *
 * For the list of contributors see $ROOTSYS/README/CREDITS.             *
 *************************************************************************/
 
#include <cstdlib>
 
#include "Riostream.h"
#include "TH1K.h"
#include "TMath.h"
 
/** \class TH1K
TH1K class supports the nearest K Neighbours method, widely used in cluster analysis.
This method is especially useful for small statistics.
In this method :
 
      DensityOfProbability ~ 1/DistanceToNearestKthNeighbour
      Ctr TH1K::TH1K(name,title,nbins,xlow,xup,K=0)
      differs from TH1F only by "K"
      K - is the order of K Neighbours method, usually >=3
      K = 0, means default, where K is selected by TH1K in such a way
             that DistanceToNearestKthNeighbour > BinWidth and K >=3
 
This class has been implemented by Victor Perevoztchikov <perev@bnl.gov>
*/
 
ClassImp(TH1K);
 
 
////////////////////////////////////////////////////////////////////////////////
/// Constructor.
 
TH1K::TH1K()
{
   fDimension = 1;
}
 
 
////////////////////////////////////////////////////////////////////////////////
/// Create a 1-Dim histogram with fix bins of type float
/// (see TH1K::TH1 for explanation of parameters)
 
TH1K::TH1K(const char *name,const char *title,Int_t nbins,Double_t xlow,Double_t xup,Int_t k)
     : TH1(name,title,nbins,xlow,xup), TArrayF(100)
{
   fDimension = 1;
   fKOrd  = k;
}
 
////////////////////////////////////////////////////////////////////////////////
/// Copy this histogram structure to newth1.
///
/// Note that this function does not copy the list of associated functions.
/// Use TObject::Clone to make a full copy of an histogram.
 
void TH1K::Copy(TObject &obj) const
{
   TH1::Copy(obj);
   ((TH1K&)obj).fNIn = fNIn;
}
 
////////////////////////////////////////////////////////////////////////////////
/// Increment bin with abscissa X by 1.
///
/// if x is less than the low-edge of the first bin, the Underflow bin is incremented
/// if x is greater than the upper edge of last bin, the Overflow bin is incremented
///
/// If the storage of the sum of squares of weights has been triggered,
/// via the function Sumw2, then the sum of the squares of weights is incremented
/// by 1 in the bin corresponding to x.
 
Int_t TH1K::Fill(Double_t x)
{
   fReady = 0;
   Int_t bin;
   fEntries++;
   bin =fXaxis.FindBin(x);
   if (bin == 0 || bin > fXaxis.GetNbins()) {
      if (!GetStatOverflowsBehaviour()) return -1;
   }
   ++fTsumw;
   ++fTsumw2;
   fTsumwx  += x;
   fTsumwx2 += x*x;
   fReady = 0;
   if (fNIn == fN) Set(fN*2);
   AddAt(x,fNIn++);
   return bin;
}
 
 
////////////////////////////////////////////////////////////////////////////////
/// Return content of global bin number bin.
 
Double_t TH1K::GetBinContent(Int_t bin) const
{
   if (!fReady) {
      ((TH1K*)this)->Sort();
      ((TH1K*)this)->fReady=1;
   }
   if (!fNIn)   return 0.;
   float x = GetBinCenter(bin);
   int left = TMath::BinarySearch(fNIn,fArray,x);
   int jl=left,jr=left+1,nk,nkmax =fKOrd;
   float fl,fr,ff=0.,ffmin=1.e-6;
   if (!nkmax) {nkmax = 3; ffmin = GetBinWidth(bin);}
   if (nkmax >= fNIn) nkmax = fNIn-1;
   for (nk = 1; nk <= nkmax || ff <= ffmin; nk++) {
      fl = (jl>=0  ) ? TMath::Abs(fArray[jl]-x) : 1.e+20;
      fr = (jr<fNIn) ? TMath::Abs(fArray[jr]-x) : 1.e+20;
      if (jl<0 && jr>=fNIn) break;
      if (fl < fr) { ff = fl; jl--;}
      else         { ff = fr; jr++;}
   }
   ((TH1K*)this)->fKCur = nk - 1;
   return fNIn * 0.5*fKCur/((float)(fNIn+1))*GetBinWidth(bin)/ff;
}
 
 
////////////////////////////////////////////////////////////////////////////////
/// Return content of global bin error.
 
Double_t TH1K::GetBinError(Int_t bin) const
{
   return TMath::Sqrt(((double)(fNIn-fKCur+1))/((fNIn+1)*(fKCur-1)))*GetBinContent(bin);
}
 
 
////////////////////////////////////////////////////////////////////////////////
/// Reset.
 
void   TH1K::Reset(Option_t *option)
{
   fNIn   =0;
   fReady = 0;
   TH1::Reset(option);
}
 
 
////////////////////////////////////////////////////////////////////////////////
/// Save primitive as a C++ statement(s) on output stream out
/// Note the following restrictions in the code generated:
///  - variable bin size not implemented, not supported by TH1K
 
void TH1K::SavePrimitive(std::ostream &out, Option_t *option /*= ""*/)
{
   TString hname = ProvideSaveName(option);
 
   out << "   \n";
   out << "   " << ClassName() << " *" << hname << " = new " << ClassName() << "(\"" << GetName() << "\", \""
       << TString(GetTitle()).ReplaceSpecialCppChars() << "\"," << GetXaxis()->GetNbins() << ","
       << GetXaxis()->GetXmin() << "," << GetXaxis()->GetXmax() << "," << fKOrd << ");\n";
 
   if (fNIn) {
      std::vector<Double_t> content(fNIn);
      for (int i = 0; i < fNIn; i++)
         content[i] = fArray[i];
 
      TString arrname = SavePrimitiveArray(out, hname, fNIn, content.data());
      out << "   for(Int_t i = 0; i < " << fNIn << "; i++)\n";
      out << "      " << hname << "->Fill(" << arrname << "[i]);\n";
   }
 
   TH1::SavePrimitiveHelp(out, hname, option);
}
 
////////////////////////////////////////////////////////////////////////////////
/// Compare.
 
static int TH1K_fcompare(const void *f1,const void *f2)
{
   if (*((float*)f1) < *((float*)f2)) return -1;
   if (*((float*)f1) > *((float*)f2)) return  1;
   return 0;
}
 
 
////////////////////////////////////////////////////////////////////////////////
/// Sort.
 
void TH1K::Sort()
{
   if (fNIn<2) return;
   qsort(GetArray(),fNIn,sizeof(Float_t),&TH1K_fcompare);
}