xpolin2.c

Numerical Recipes in C的源代码

/* Driver for routine polin2 */

#include <stdio.h>
#include <math.h>
#include "nr.h"
#include "nrutil.h"

#define N 5
#define PI 3.1415926

main()
{
	int i,j;
	float dy,f,x1,x2,y,*x1a,*x2a,**ya;

	x1a=vector(1,N);
	x2a=vector(1,N);
	ya=matrix(1,N,1,N);
	for (i=1;i<=N;i++) {
		x1a[i]=i*PI/N;
		for (j=1;j<=N;j++) {
			x2a[j]=1.0*j/N;
			ya[i][j]=sin(x1a[i])*exp(x2a[j]);
		}
	}
	/* test 2-dimensional interpolation */
	printf("\nTwo dimensional interpolation of sin(x1)exp(x2)\n");
	printf("%9s %12s %13s %16s %11s\n",
		"x1","x2","f(x)","interpolated","error");
	for (i=1;i<=4;i++) {
		x1=(-0.1+i/5.0)*PI;
		for (j=1;j<=4;j++) {
			x2 = -0.1+j/5.0;
			f=sin(x1)*exp(x2);
			polin2(x1a,x2a,ya,N,N,x1,x2,&y,&dy);
			printf("%12.6f %12.6f %12.6f %12.6f %15.6f\n",
				x1,x2,f,y,dy);
		}
		printf ("***********************************\n");
	}
	free_matrix(ya,1,N,1,N);
	free_vector(x2a,1,N);
	free_vector(x1a,1,N);
	return 0;
}