#include <iostream>
#include "TStyle.h"
#include "TH2D.h"
#include "TCanvas.h"
#include "TMath.h"

Functions
Int_t	FindTheBin (TH2 *lookup_table, Float_t value_x, Float_t value_y, Int_t &bin_x, Int_t &bin_y)

Double_t	GetValueInZ (TH2 *lookup_table, Float_t value_x, Float_t value_y, Bool_t use_interpolation=kFALSE)

void	TestIt (Bool_t use_interpolation=kFALSE)

Function Documentation

Int_t FindTheBin	(	TH2 *	lookup_table,
		Float_t	value_x,
		Float_t	value_y,
		Int_t &	bin_x,
		Int_t &	bin_y
	)

Definition at line 17 of file lookupTable.cxx.

Referenced by GetValueInZ().

 {
  bin_x = lookup_table->GetXaxis()->FindBin(value_x);
  bin_y = lookup_table->GetYaxis()->FindBin(value_y);
 
  if ((bin_x < 1) || (bin_x > lookup_table->GetXaxis()->GetNbins()))
   {
    bin_x = -1; bin_y = -1; 
    return -1;
   }
 
  if ((bin_y < 1) || (bin_y > lookup_table->GetYaxis()->GetNbins()))
   {
    bin_x = -1; bin_y = -1; 
    return -2;
   }
 
  return 0; // Succes
 } 

Double_t GetValueInZ	(	TH2 *	lookup_table,
		Float_t	value_x,
		Float_t	value_y,
		Bool_t	use_interpolation = `kFALSE`
	)

Definition at line 43 of file lookupTable.cxx.

References FindTheBin().

Referenced by TestIt().

 {
 
  if (use_interpolation)
   {
    //
    // Use the interpolarion routine of ROOT:
    // Interpolate approximates the value via bilinear
    // interpolation based on the four nearest bin centers
    // see Wikipedia, Bilinear Interpolation
    // Andy Mastbaum 10/8/2008
    // vaguely based on R.Raja 6-Sep-2008
    //
    return (lookup_table->Interpolate(value_x,value_y));
   }
  else
   {
 
    Int_t binx, biny, retval;
 
    retval = FindTheBin(lookup_table, value_x, value_y, binx, biny);
    if (retval)
     {
      cout << "<E> Error in FindTheBin, check your table and input values!!!!: " << retval << endl;
      return 0;
     }
 
    return (lookup_table->GetBinContent(binx,biny));
   }
  return 0;
 }

void TestIt ( Bool_t use_interpolation = kFALSE )

Definition at line 75 of file lookupTable.cxx.

References c, Double_t, GetValueInZ(), h1, h2, and i.

 {
  //
  // Create two 2D spectrum, not equal in binning!
  // Try to set the interpolation flag to kTRUE and compare with kFALSE
  //
 
  gStyle->SetPalette(1);
 
  Double_t xlowarray_1[] = {0,10,20,30,40,50,60,70,80,90,100};
  Double_t ylowarray_1[] = {0,10,20,30,40,50,60,70,80,90,100};
 
  TH2D *h1 = new TH2D("h1","Input spectrum",
                      (sizeof(xlowarray_1)/sizeof(Double_t))-1,xlowarray_1,
                      (sizeof(ylowarray_1)/sizeof(Double_t))-1,ylowarray_1);
 
  Double_t xlowarray_2[] = {0,10,20,30,35,40,45,46,47,48,49,50,51,52,53,54,55,60,65,70,80,90,100};
  Double_t ylowarray_2[] = {0,10,20,30,35,40,45,46,47,48,49,50,51,52,53,54,55,60,65,70,80,90,100};
 
  TH2D *h2 = new TH2D("h2","Check spectrum",
                      (sizeof(xlowarray_2)/sizeof(Double_t))-1,xlowarray_2,
                      (sizeof(ylowarray_2)/sizeof(Double_t))-1,ylowarray_2);
 
  //
  // Fill Input spectrum with random numbers
  //
 
  for (Int_t i = 1; i < (h1->GetXaxis()->GetNbins() + 1); i++)
    {
     for (Int_t j = 1; j < (h1->GetYaxis()->GetNbins() + 1); j++)
      {
        h1->SetBinContent(i,j,
                          TMath::Gaus(h1->GetXaxis()->GetBinCenter(j),50,20)+
                          TMath::Gaus(h1->GetXaxis()->GetBinCenter(i),50,10));
      } 
    }
 
  //
  // Fill check spectrum using lookup
  //
 
  Double_t valx, valy, valz;
  for (Int_t i = 1; i < (h2->GetXaxis()->GetNbins() + 1); i++)
    {
     valx = h2->GetXaxis()->GetBinCenter(i);
     for (Int_t j = 1; j < (h2->GetYaxis()->GetNbins() + 1); j++)
      {
        valy = h2->GetYaxis()->GetBinCenter(j);
        cout << "<I> Checking (" << valx << "," << valy << ")" << endl; 
        valz = GetValueInZ((TH2*) h1, valx, valy, use_interpolation);
        h2->SetBinContent(i,j,valz);
      } 
    }
 
 //
 // At this point h1 should be equal to h2, check it yourself!
 //
 
   TCanvas *c = new TCanvas();
   c->Divide(1,2);
   c->cd(1);
   h1->Draw("zcol");
   c->cd(2);
   h2->Draw("zcol");
 
   cout << "Compare TestIt(kTRUE) with TestIt(kFALSE), interpolation really improves! Cool, heh!" << endl;
 }

Functions

Function Documentation