Re: Real-data DFT in Octave

[Sergei Steshenko]

>________________________________
> From: Doug Stewart <address@hidden>
>To: Sergei Steshenko <address@hidden> 
>Cc: Torbjörn Rathsman <address@hidden>; "address@hidden" <address@hidden> 
>Sent: Saturday, October 6, 2012 3:46 PM
>Subject: Re: Real-data DFT in Octave
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>On Sat, Oct 6, 2012 at 9:35 AM, Sergei Steshenko <address@hidden> wrote:
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>>----- Original Message -----
>>> From: Torbjörn Rathsman <address@hidden>
>>> To: address@hidden
>>> Cc:
>>> Sent: Saturday, October 6, 2012 3:18 PM
>>> Subject: Real-data DFT in Octave
>>>
>>> Is it possible to without much effort call the real to complex dft routins 
>>> from
>>> octave. It is easier to manipulate the spectrum that way, since i am 
>>> guarantied
>>> that the mirror part becomes correct. The purpose in this case is to compute
>>> filtered derivative of second order.
>>> _______________________________________________
>>> Help-octave mailing list
>>> address@hidden
>>> https://mailman.cae.wisc.edu/listinfo/help-octave
>>
>>
>>I am not sure what the problem is, but dealing with real input data I use 
>>'conj' and 'fliplr' in the end when I need to produce mirrored spoectrum for 
>>inverse FFT.
>>
>>Regards,
>>  Sergei.
>>
>>
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>fft works for me
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>a=randn(100,1);
>b=fft(a);
>c=ifft(b);
>d=real(c);
>e=a-d;
>e(1:10)
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>this gives close to zero,which is good.
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>-- 
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>DAS
>
>https://linuxcounter.net/user/206392.html
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I didn't mean 'fft', 'ifft' were not working.

Your example does not include application of filter. Application of filter 
makes sense only on left half of the spectrum since the right half is complex 
conjugate of the left half.

Regards,
  Sergei.



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