/* Robert Grumbine */

/* Program to illustrate error average in support of article 
http://moregrumbinescience.blogspot.com/2010/03/ */

/*  10 March 2010 */


#include <stdio.h>
#include <stdlib.h>

#define NTRIALS 365
#define NCOINS    8

int main(void) {
  float trials[NTRIALS];
  float sample[NCOINS];
  float toss, sum, grandsum, errsize;
  int i, j;

  srand(0);
  
  errsize = 0.1;
  grandsum = 0.0;
  for (i = 0; i < NTRIALS; i++) {
    sum = 0.;
    for (j = 0; j < NCOINS; j++) {
      toss = (float) rand() / (float) RAND_MAX; 
      if (toss > 0.5) {
        sample[j] = +errsize;
      }
      else {
        sample[j] = -errsize;
      }
      sum += sample[j];
    }
    printf("Trial %4d error %4.1f\n",i,sum);
    trials[i] = sum;
    grandsum += sum;
  }
  printf("Total error after %d trials is %f, average is %f\n",
          NTRIALS, grandsum, grandsum/(float)NTRIALS);

  return 0;
}