ftest.c

Numerical Recipes in C的源代码

void ftest(float data1[], unsigned long n1, float data2[], unsigned long n2,
	float *f, float *prob)
{
	void avevar(float data[], unsigned long n, float *ave, float *var);
	float betai(float a, float b, float x);
	float var1,var2,ave1,ave2,df1,df2;

	avevar(data1,n1,&ave1,&var1);
	avevar(data2,n2,&ave2,&var2);
	if (var1 > var2) {
		*f=var1/var2;
		df1=n1-1;
		df2=n2-1;
	} else {
		*f=var2/var1;
		df1=n2-1;
		df2=n1-1;
	}
	*prob = 2.0*betai(0.5*df2,0.5*df1,df2/(df2+df1*(*f)));
	if (*prob > 1.0) *prob=2.0-*prob;
}