//========================================================= file = lec5.c =====
//=  A program to plot a histogram of a random number generator               =
//=============================================================================
//=  Build: bcc32 lec5.c, cl lec5.c, gcc lec5.c                               =
//=---------------------------------------------------------------------------=
//=  History:  KJC (05/29/11) - Refresh from old version                      =
//=============================================================================
//----- Include files ---------------------------------------------------------
#include <stdio.h>               // Needed for printf()
#include <stdlib.h>              // Needed for rand() and RAND_MAX

//----- Include files ---------------------------------------------------------
#define NUM_BINS           20    // The number of bins in the histogram
#define NUM_SAMPLES   2000000    // The number of samples to test

//===== Main program ==========================================================
void main(void)
{
  double z;                     // Uniform random number from 0 to 1
  int    histo[NUM_BINS];       // Histogram array
  int    bin_num;               // Bin number for histogram
  int    i;                     // Loop counter

  // Initialize the histogram to all zero
  for (i=0; i<NUM_BINS; i++)
    histo[i] = 0;

  // "Plot" NUM_SAMPLES samples into histogram
  for (i=0; i<NUM_SAMPLES; i++)
  {
    // Pull a uniform RV
    z = ((double) rand() / RAND_MAX);

    // Map z to its appropriate bin
    for (bin_num=0; bin_num<NUM_BINS; bin_num++)
      if (z <= ((double) (bin_num + 1) / NUM_BINS))
      {
        histo[bin_num]++;
        break;
      }
  }

  // Output histogram values
  for (i=0; i<NUM_BINS; i++)
    printf("Bin %2d = %6d \n", i, histo[i]);
}