add numerical recipes library

lib/nr/ansi/examples/xpolint.c

@@ -0,0 +1,62 @@
+
+/* Driver for routine polint */
+
+#include <stdio.h>
+#include <math.h>
+#define NRANSI
+#include "nr.h"
+#include "nrutil.h"
+
+#define PI 3.1415926
+
+int main(void)
+{
+	int i,n,nfunc;
+	float dy,f,x,y,*xa,*ya;
+
+	printf("generation of interpolation tables\n");
+	printf(" ... sin(x)    0<x<PI\n");
+	printf(" ... exp(x)    0<x<1 \n");
+	printf("how many entries go in these tables?\n");
+	if (scanf("%d",&n) == EOF) return 1;
+	xa=vector(1,n);
+	ya=vector(1,n);
+	for (nfunc=1;nfunc<=2;nfunc++) {
+		if (nfunc == 1) {
+			printf("\nsine function from 0 to PI\n");
+			for (i=1;i<=n;i++) {
+				xa[i]=i*PI/n;
+				ya[i]=sin(xa[i]);
+			}
+		} else if (nfunc == 2) {
+			printf("\nexponential function from 0 to 1\n");
+			for (i=1;i<=n;i++) {
+				xa[i]=i*1.0/n;
+				ya[i]=exp(xa[i]);
+			}
+		} else {
+			break;
+		}
+		printf("\n%9s %13s %16s %13s\n",
+			"x","f(x)","interpolated","error");
+		for (i=1;i<=10;i++) {
+			if (nfunc == 1) {
+				x=(-0.05+i/10.0)*PI;
+				f=sin(x);
+			} else if (nfunc == 2) {
+				x=(-0.05+i/10.0);
+				f=exp(x);
+			}
+			polint(xa,ya,n,x,&y,&dy);
+			printf("%12.6f %12.6f %12.6f %4s %11f\n",
+				x,f,y," ",dy);
+		}
+		printf("\n***********************************\n");
+		printf("press RETURN\n");
+		(void) getchar();
+	}
+	free_vector(ya,1,n);
+	free_vector(xa,1,n);
+	return 0;
+}
+#undef NRANSI