/* file : variance.c
 * purpose : calculate the variance of a data set
 */

#include <math.h>

double
variance(vec,ave,len)
double	*vec;		/* pointer to the vector */
double  ave;            /* median value of the data set */
int	len;		/* length of the vector */
{
		  int i;
		  double sum,tem;

		  sum=0.0;

		  for (i=0;i<len;i++)
		  {
					 tem=vec[i]-ave;
					 tem=tem*tem;
					 sum+=tem;
		  }

		  sum=sum/len;

		  sum=sqrt(sum);

		  return(sum);
}