add numerical recipes library

lib/nr/k_and_r/recipes/polin2.c

@@ -0,0 +1,18 @@
+
+#include "nrutil.h"
+
+void polin2(x1a,x2a,ya,m,n,x1,x2,y,dy)
+float **ya,*dy,*y,x1,x1a[],x2,x2a[];
+int m,n;
+{
+	void polint();
+	int j;
+	float *ymtmp;
+
+	ymtmp=vector(1,m);
+	for (j=1;j<=m;j++) {
+		polint(x2a,ya[j],n,x2,&ymtmp[j],dy);
+	}
+	polint(x1a,ymtmp,m,x1,y,dy);
+	free_vector(ymtmp,1,m);
+}