add numerical recipes library

lib/nr/k_and_r/recipes/chder.c

@@ -0,0 +1,16 @@
+
+void chder(a,b,c,cder,n)
+float a,b,c[],cder[];
+int n;
+{
+	int j;
+	float con;
+
+	cder[n-1]=0.0;
+	cder[n-2]=2*(n-1)*c[n-1];
+	for (j=n-3;j>=0;j--)
+		cder[j]=cder[j+2]+2*(j+1)*c[j+1];
+	con=2.0/(b-a);
+	for (j=0;j<n;j++)
+		cder[j] *= con;
+}