avevar.c

Numerical Recipes in C的源代码

void avevar(data,n,ave,var)
float *ave,*var,data[];
unsigned long n;
{
	unsigned long j;
	float s,ep;

	for (*ave=0.0,j=1;j<=n;j++) *ave += data[j];
	*ave /= n;
	*var=ep=0.0;
	for (j=1;j<=n;j++) {
		s=data[j]-(*ave);
		ep += s;
		*var += s*s;
	}
	*var=(*var-ep*ep/n)/(n-1);
}