hist_08.cc

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// file: $isip/class/numeric/Histogram/hist_08.cc
// version: $Id: hist_08.cc,v 1.1 2001/02/01 16:47:51 hamaker Exp $
//

// isip include files
//
#include "Histogram.h"

// method: pdf
//
// arguments:
//  VectorDouble& pdf: (output) pdf of histogram data
//
// return: boolean value indicating status
//
// this method computes the probability density function given counts from
// the histogram data
//
boolean Histogram::pdf(VectorDouble& pdf_a) const {

  // make sure the histogram has been initialized
  //
  if ((bins_d.length() == 0) || (counts_d.length() != bins_d.length())) {
    return Error::handle(name(), L"update", ERR_BINS, __FILE__, __LINE__);
  }

  // copy the counts over
  //
  pdf_a.assign(counts_d);

  // divide by the sum of all counts
  //
  double sum = pdf_a.sum();
  if (sum != 0) {
    pdf_a.div(sum);
  }
  
  // exit gracefully
  //
  return true;
}

// method: cdf
//
// arguments:
//  VectorDouble& cdf: (output) cdf of histogram data
//
// return: boolean value indicating status
//
// this method computes the cumulative density function given counts from
// the histogram data
//
boolean Histogram::cdf(VectorDouble& cdf_a) const {

  // make sure the histogram has been initialized
  //
  if ((bins_d.length() == 0) || (counts_d.length() != bins_d.length())) {
    return Error::handle(name(), L"update", ERR_BINS, __FILE__, __LINE__);
  }

  // copy the counts over
  //
  cdf_a.assign(counts_d);

  // compute the cdf of the counts
  //
  double sum = cdf_a.sum();
  long length = cdf_a.length();
  for (long i = 1; i < length; i++) {
    cdf_a(i) += cdf_a(i-1);
  }

  // normalize
  //
  if (sum != 0) {
    cdf_a.div(sum);
  }

  // manually set the last bin
  //
  cdf_a(length - 1) = 1;
  
  // exit gracefully
  //
  return true;
}