50 lines
894 B
C++
50 lines
894 B
C++
#include <cmath>
|
|
#include "nr.h"
|
|
using namespace std;
|
|
|
|
void NR::four1(Vec_IO_DP &data, const int isign)
|
|
{
|
|
int n,mmax,m,j,istep,i;
|
|
DP wtemp,wr,wpr,wpi,wi,theta,tempr,tempi;
|
|
|
|
int nn=data.size()/2;
|
|
n=nn << 1;
|
|
j=1;
|
|
for (i=1;i<n;i+=2) {
|
|
if (j > i) {
|
|
SWAP(data[j-1],data[i-1]);
|
|
SWAP(data[j],data[i]);
|
|
}
|
|
m=nn;
|
|
while (m >= 2 && j > m) {
|
|
j -= m;
|
|
m >>= 1;
|
|
}
|
|
j += m;
|
|
}
|
|
mmax=2;
|
|
while (n > mmax) {
|
|
istep=mmax << 1;
|
|
theta=isign*(6.28318530717959/mmax);
|
|
wtemp=sin(0.5*theta);
|
|
wpr = -2.0*wtemp*wtemp;
|
|
wpi=sin(theta);
|
|
wr=1.0;
|
|
wi=0.0;
|
|
for (m=1;m<mmax;m+=2) {
|
|
for (i=m;i<=n;i+=istep) {
|
|
j=i+mmax;
|
|
tempr=wr*data[j-1]-wi*data[j];
|
|
tempi=wr*data[j]+wi*data[j-1];
|
|
data[j-1]=data[i-1]-tempr;
|
|
data[j]=data[i]-tempi;
|
|
data[i-1] += tempr;
|
|
data[i] += tempi;
|
|
}
|
|
wr=(wtemp=wr)*wpr-wi*wpi+wr;
|
|
wi=wi*wpr+wtemp*wpi+wi;
|
|
}
|
|
mmax=istep;
|
|
}
|
|
}
|