67 lines
1.4 KiB
C
67 lines
1.4 KiB
C
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/* Driver for routine twofft */
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#include <stdio.h>
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#include <math.h>
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#define NRANSI
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#include "nr.h"
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#include "nrutil.h"
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#define N 32
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#define N2 (2*N)
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#define PER 8
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#define PI 3.1415926
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void prntft(float data[],unsigned long nn)
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{
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unsigned long n;
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printf("%4s %13s %13s %12s %13s\n",
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"n","real(n)","imag.(n)","real(N-n)","imag.(N-n)");
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printf(" 0 %14.6f %12.6f %12.6f %12.6f\n",
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data[1],data[2],data[1],data[2]);
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for (n=3;n<=nn+1;n+=2) {
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printf("%4lu %14.6f %12.6f %12.6f %12.6f\n",
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((n-1)/2),data[n],data[n+1],
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data[2*nn+2-n],data[2*nn+3-n]);
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}
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printf(" press return to continue ...\n");
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(void) getchar();
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return;
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}
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int main(void)
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{
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unsigned long i;
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int isign;
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float *data1,*data2,*fft1,*fft2;
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data1=vector(1,N);
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data2=vector(1,N);
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fft1=vector(1,N2);
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fft2=vector(1,N2);
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for (i=1;i<=N;i++) {
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data1[i]=floor(0.5+cos(i*2.0*PI/PER));
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data2[i]=floor(0.5+sin(i*2.0*PI/PER));
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}
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twofft(data1,data2,fft1,fft2,N);
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printf("Fourier transform of first function:\n");
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prntft(fft1,N);
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printf("Fourier transform of second function:\n");
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prntft(fft2,N);
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/* Invert transform */
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isign = -1;
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four1(fft1,N,isign);
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printf("inverted transform = first function:\n");
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prntft(fft1,N);
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four1(fft2,N,isign);
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printf("inverted transform = second function:\n");
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prntft(fft2,N);
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free_vector(fft2,1,N2);
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free_vector(fft1,1,N2);
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free_vector(data2,1,N);
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free_vector(data1,1,N);
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return 0;
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}
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#undef NRANSI
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