Re: Real-data DFT in Octave

[Torbjörn Rathsman]

Sergei Steshenko skrev 2012-10-06 15:35:
> ----- 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.
Do you mean

    Y=fft(y)';
    for k=1:length(Y)
        if(k<=1024)
            Y(k)=(k-1)*(k-1)*Y(k)/N;
        else
            Y(k)=0;
        end
    end

    Y=Y+conj( fliplr(Y) );
? cannot get it work.