The C/C++ version of SNP-HWE can be downloaded by following the link below and right clicking on the source code. Once this function has been incorporated into your program, it can be called by passing observed counts for each of the three SNP genotypes (heterozygote, homozygote_1, and homozygote_2) as function arguments. The code snippet below illustrates a typical calling sequence to read in genotype counts listed in a text file ("genotype_counts_c.txt") and perform the exact test of Hardy-Weinberg on each marker:

genotype_counts_c.txt:

MARKER_1  100    3    5
MARKER_2   57   14   50
MARKER_3   31   32   51
MARKER_4   47    3    5
MARKER_5  150   32   55
MARKER_6  122    7   32
MARKER_7   99    3   14
MARKER_8  146   13   54
MARKER_9  177  100   57
MARKER_10 184   57  155

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

double SNPHWE(int obs_hets, int obs_hom1, int obs_hom2);

int main(int argc, char * argv[])
   {
   FILE * test_file = fopen("genotype_counts_c.txt", "rt");
   if (test_file == NULL)
      {
      printf("Unable to open test file");
      exit(EXIT_FAILURE);
      }
   
   int hets, homs1, homs2;
   double p_value;
   char name[100];

   while (!feof(test_file))
      {
      fscanf(test_file, "%s %d %d %d\n", name, &hets, &homs1, &homs2);
      p_value = SNPHWE(hets, homs1, homs2);
      printf("P-value for %s: %lg\n", name, p_value);
      }
   }

Source distribution

    SNP-HWE (C/C++)