add numerical recipes library

lib/nr/ansi/recipes/chstwo.c

@@ -0,0 +1,19 @@
+
+void chstwo(float bins1[], float bins2[], int nbins, int knstrn, float *df,
+	float *chsq, float *prob)
+{
+	float gammq(float a, float x);
+	int j;
+	float temp;
+
+	*df=nbins-knstrn;
+	*chsq=0.0;
+	for (j=1;j<=nbins;j++)
+		if (bins1[j] == 0.0 && bins2[j] == 0.0)
+			--(*df);
+		else {
+			temp=bins1[j]-bins2[j];
+			*chsq += temp*temp/(bins1[j]+bins2[j]);
+		}
+	*prob=gammq(0.5*(*df),0.5*(*chsq));
+}