#include <SimpleHistogramGenerator.h>

Public Member Functions
int	binarySearch (const int &n, const std::vector< float > &array, const double &value) const

double	generate (RandomEngineAndDistribution const *) const
	The random generation. More...

	SimpleHistogramGenerator (TH1 *histo)

virtual	~SimpleHistogramGenerator ()
	Default destructor. More...

Private Attributes
double	binWidth

std::vector< float >	integral
	Integral. More...

int	nBins
	Pointer to the histogram. More...

double	nEntries
	Number of entries. More...

double	xMax

double	xMin

Detailed Description

Definition at line 21 of file SimpleHistogramGenerator.h.

Constructor & Destructor Documentation

SimpleHistogramGenerator::SimpleHistogramGenerator ( TH1 * histo )

Constructor that perform the necessary integration and inversion steps xmin and xmax are the generation bounds, n is the internal table size and iter is the number of iterations for the numerical part.

Definition at line 8 of file SimpleHistogramGenerator.cc.

References mps_fire::i, integral, nBins, and nEntries.

     :  //myHisto(histo),
       //theXaxis(histo->GetXaxis()),
       nBins(histo->GetXaxis()->GetNbins()),
       xMin(histo->GetXaxis()->GetXmin()),
       xMax(histo->GetXaxis()->GetXmax()),
       binWidth((xMax - xMin) / (float)nBins) {
   integral.reserve(nBins + 2);
   integral.push_back(0.);
   for (int i = 1; i <= nBins; ++i)
     integral.push_back(integral[i - 1] + histo->GetBinContent(i));
   integral.push_back(integral[nBins]);
   nEntries = integral[nBins + 1];
   for (int i = 1; i <= nBins; ++i)
     integral[i] /= nEntries;
 }

virtual SimpleHistogramGenerator::~SimpleHistogramGenerator ( )

inlinevirtual

Default destructor.

Definition at line 29 of file SimpleHistogramGenerator.h.

29 {}

Member Function Documentation

int SimpleHistogramGenerator::binarySearch	(	const int &	n,
		const std::vector< float > &	array,
		const double &	value
	)		const

Definition at line 37 of file SimpleHistogramGenerator.cc.

Referenced by generate().

                                                                                                                  {
   // Binary search in an array of n values to locate value.
   //
   // Array is supposed  to be sorted prior to this call.
   // If match is found, function returns position of element.
   // If no match found, function gives nearest element smaller than value.
 
   int nabove, nbelow, middle;
   nabove = n + 1;
   nbelow = 0;
   while (nabove - nbelow > 1) {
     middle = (nabove + nbelow) / 2;
     if (value == array[middle - 1])
       return middle - 1;
     if (value < array[middle - 1])
       nabove = middle;
     else
       nbelow = middle;
   }
   return nbelow - 1;
 }

double SimpleHistogramGenerator::generate ( RandomEngineAndDistribution const * random ) const

The random generation.

Definition at line 25 of file SimpleHistogramGenerator.cc.

References binarySearch(), binWidth, RandomEngineAndDistribution::flatShoot(), integral, nBins, diffTwoXMLs::r1, x, and xMin.

Referenced by PixelTemplateSmearerBase::smearHit(), and PixelTemplateSmearerBase::smearMergeGroup().

                                                                                          {
   // return a random number distributed according the histogram bin contents.
   // NB Only valid for 1-d histograms, with fixed bin width.
 
   double r1 = random->flatShoot();
   int ibin = binarySearch(nBins, integral, r1);
   double x = xMin + (double)(ibin)*binWidth;
   if (r1 > integral[ibin])
     x += binWidth * (r1 - integral[ibin]) / (integral[ibin + 1] - integral[ibin]);
   return x;
 }