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spirid
 Post subject: FFT error
PostPosted: Sun Nov 25, 2012 8:29 am 
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Joined: Sun Nov 25, 2012 8:22 am
Posts: 5
Code:
alglib.complex[] z = new alglib.complex[xint.LongLength]; // xint - array sources data (2048 samples)
alglib.complex f = z[0];
alglib.fft.fftr1d(xint, xint.LongLength, f); // Error in IDE Visual Studio
Help me, please
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Sergey.Bochkanov
 Post subject: Re: FFT error
PostPosted: Mon Nov 26, 2012 4:56 am 
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Joined: Fri May 07, 2010 7:06 am
Posts: 927
Last parameter of fftr1d must be complex array passed as out-parameter. Does it solves your problem?
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spirid
 Post subject: Re: FFT error
PostPosted: Tue Nov 27, 2012 7:35 am 
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Joined: Sun Nov 25, 2012 8:22 am
Posts: 5
Corrected the code:
alglib.fft.fftr1d(xint, 2048, ref z);
and the error disappeared. Now I do not know how to get out of the complex (z) real (Rez) and imaginary (Imz) parts for the amplitude spectrum to build.
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Sergey.Bochkanov
 Post subject: Re: FFT error
PostPosted: Tue Nov 27, 2012 10:25 am 
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Z[j].x stores real part, Z[j].y stores imaginary part.
J-th element of Z is equal to SUM(X[k]*exp(-2*pi*sqrt(-1)*j*k/N), k = 0..N-1) (expression is given to distinguish between different kinds of FFT)
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spirid
 Post subject: Re: FFT error
PostPosted: Tue Nov 27, 2012 7:23 pm 
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Thanks a lot! After correcting the code it work properly!
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