xgasdev.c

< C语言数值算法程序大全>>配套程序

/* Driver for routine gasdev */

#include <stdio.h>
#define NRANSI
#include "nr.h"

#define N 20
#define NOVER2 (N/2)
#define NPTS 10000
#define ISCAL 400
#define LLEN 50

int main(void)
{
	char words[LLEN+1];
	int i,j,k,klim,dist[N+1];
	long idum=(-13);
	float dd,x;

	for (j=0;j<=N;j++) dist[j]=0;
	for (i=1;i<=NPTS;i++) {
		x=0.25*N*gasdev(&idum);
		j=(int)(x > 0 ? x+0.5 : x-0.5);
		if ((j >= -NOVER2) && (j <= NOVER2)) ++dist[j+NOVER2];
	}
	printf("Normally distributed deviate of %6d points\n",NPTS);
	printf ("%5s %10s %9s\n","x","p(x)","graph:");
	for (j=0;j<=N;j++) {
		dd=(float) dist[j]/NPTS;
		for (k=1;k<=LLEN;k++) words[k]=' ';
		klim=(int) (ISCAL*dd);
		if (klim > LLEN)  klim=LLEN;
		for (k=1;k<=klim;k++) words[k]='*';
		printf("%8.4f %8.4f  ",j/(0.25*N),dd);
		for (k=1;k<=LLEN;k++) printf("%c",words[k]);
		printf("\n");
	}
	return 0;
}
#undef NRANSI