xfourn.c

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/* Driver for routine fourn */

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

#define NDIM 3
#define NDAT2 1024

int main(void)
{
	int isign;
	long idum=(-23);
	unsigned long i,j,k,l,ndum=2,*nn;
	float *data1,*data2;

	nn=lvector(1,NDIM);
	data1=vector(1,NDAT2);
	data2=vector(1,NDAT2);
	for (i=1;i<=NDIM;i++) nn[i]=(ndum <<= 1);
	for (i=1;i<=nn[3];i++)
		for (j=1;j<=nn[2];j++)
			for (k=1;k<=nn[1];k++) {
				l=k+(j-1)*nn[1]+(i-1)*nn[2]*nn[1];
				l=(l<<1)-1;
				/* real part of component */
				data2[l]=data1[l]=2*ran1(&idum)-1;
				/* imaginary part of component */
				l++;
				data2[l]=data1[l]=2*ran1(&idum)-1;
			}
	isign=1;
	fourn(data2,nn,NDIM,isign);
	/* here would be any processing to be done in Fourier space */
	isign = -1;
	fourn(data2,nn,NDIM,isign);
	printf("Double 3-dimensional transform\n\n");
	printf("%22s %24s %20s\n",
		"Double transf.","Original data","Ratio");
	printf("%10s %13s %12s %13s %11s %13s\n\n",
		"real","imag.","real","imag.","real","imag.");
	for (i=1;i<=4;i++) {
		k=2*(j=2*i);
		l=k+(j-1)*nn[1]+(i-1)*nn[2]*nn[1];
		l=(l<<1)-1;
		printf("%12.2f %12.2f %10.2f %12.2f %14.2f %12.2f\n",
			data2[l],data2[l+1],data1[l],data1[l+1],
			data2[l]/data1[l],data2[l+1]/data1[l+1]);
	}
	printf("\nThe product of transform lengths is: %4lu\n",nn[1]*nn[2]*nn[3]);
	free_vector(data2,1,NDAT2);
	free_vector(data1,1,NDAT2);
	free_lvector(nn,1,NDIM);
	return 0;
}
#undef NRANSI