add numerical recipes library

lib/nr/k_and_r/recipes/polcof.c

@@ -0,0 +1,37 @@
+
+#include <math.h>
+#include "nrutil.h"
+
+void polcof(xa,ya,n,cof)
+float cof[],xa[],ya[];
+int n;
+{
+	void polint();
+	int k,j,i;
+	float xmin,dy,*x,*y;
+
+	x=vector(0,n);
+	y=vector(0,n);
+	for (j=0;j<=n;j++) {
+		x[j]=xa[j];
+		y[j]=ya[j];
+	}
+	for (j=0;j<=n;j++) {
+		polint(x-1,y-1,n+1-j,0.0,&cof[j],&dy);
+		xmin=1.0e38;
+		k = -1;
+		for (i=0;i<=n-j;i++) {
+			if (fabs(x[i]) < xmin) {
+				xmin=fabs(x[i]);
+				k=i;
+			}
+			if (x[i]) y[i]=(y[i]-cof[j])/x[i];
+		}
+		for (i=k+1;i<=n-j;i++) {
+			y[i-1]=y[i];
+			x[i-1]=x[i];
+		}
+	}
+	free_vector(y,0,n);
+	free_vector(x,0,n);
+}