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real_fft works

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Mark Borgerding 2003-11-12 02:49:04 +00:00
parent 206e28f11c
commit 673c7bafa4
1 changed files with 11 additions and 21 deletions
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30
fft.py
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@ -38,34 +38,24 @@ def fft(f):
return Fout
def real_fft( f ):
broken
N = len(f) / 2
res = f[::2]
ims = f[1::2]
fp = [ complex(r,i) for r,i in zip(res,ims) ]
Fp = fft( fp )
Fpr = [ c.real for c in Fp ]
Fpi = [ c.imag for c in Fp ]
F = []
for k in range(N):
s2 = ( Fp[k] + Fp[-k] ) * .5
d2 = ( Fp[k] - Fp[-k] ).conjugate() * .5
F1k = complex( s2.real , d2.imag )
F2k = complex( s2.imag , d2.real )
F.append( F1k + e ** ( -j*pi*k/N ) * F2k )
F1 = [complex(0,0)]*(N+1)
F2 = [complex(0,0)]*(N+1)
F1[0] = complex( Fpr[0] , 0 )
F2[0] = complex( Fpi[0] , 0 )
#F1[N] = complex( Fpr[N] , 0 )
#F2[N] = complex( Fpi[N] , 0 )
for k in range(1,N):
F1[k] = complex( (Fpr[k]+Fpr[N-k])/2 , j*(Fpi[k]-Fpi[N-k])/2 )
F2[k] = complex( (Fpi[k]+Fpi[N-k])/2 , j*(Fpr[k]-Fpr[N-k])/2 )
F = [ complex(0,0) ] * ( N + 1 )
for k in range(N+1):
F[k] = F1[k] + e ** ( j*pi*k/N ) * F2[k]
F.append( complex( Fp[0].real - Fp[0].imag , 0 ) )
return F
def test(f=range(1024),ntimes=10):