38 lines
659 B
C++
38 lines
659 B
C++
#include <cmath>
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#include "nr.h"
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using namespace std;
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void NR::cosft1(Vec_IO_DP &y)
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{
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const DP PI=3.141592653589793238;
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int j;
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DP sum,y1,y2,theta,wi=0.0,wpi,wpr,wr=1.0,wtemp;
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int n=y.size()-1;
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Vec_DP yy(n);
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theta=PI/n;
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wtemp=sin(0.5*theta);
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wpr = -2.0*wtemp*wtemp;
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wpi=sin(theta);
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sum=0.5*(y[0]-y[n]);
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yy[0]=0.5*(y[0]+y[n]);
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for (j=1;j<n/2;j++) {
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wr=(wtemp=wr)*wpr-wi*wpi+wr;
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wi=wi*wpr+wtemp*wpi+wi;
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y1=0.5*(y[j]+y[n-j]);
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y2=(y[j]-y[n-j]);
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yy[j]=y1-wi*y2;
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yy[n-j]=y1+wi*y2;
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sum += wr*y2;
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}
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yy[n/2]=y[n/2];
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realft(yy,1);
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for (j=0;j<n;j++) y[j]=yy[j];
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y[n]=y[1];
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y[1]=sum;
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for (j=3;j<n;j+=2) {
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sum += y[j];
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y[j]=sum;
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}
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}
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