[SciPy-User] Is the second half of np.fft.fft the negative frequencies?

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[SciPy-User] Is the second half of np.fft.fft the negative frequencies?

Matti Viljamaa
I’m having the following problem


My question is:

in


are samples [0, 512] the positive frequencies and [513, 1024] the negative frequencies (in two-sided FFT).
I.e. that to be correct the plot should actually look like [513, 1024] is [-512, 0] and [0,512] is [0,512], but is this the np.fft.fft way to return the negative frequencies (i.e in the latter half of the fft result)?

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Re: Is the second half of np.fft.fft the negative frequencies?

Robert Kern-2
On Wed, Aug 31, 2016 at 8:11 AM, Matti Viljamaa <[hidden email]> wrote:

>
> I’m having the following problem
>
> http://dsp.stackexchange.com/questions/33982/problem-with-windowing-method-result-seems-shifted
>
> My question is:
>
> in
>
> http://i.stack.imgur.com/fYFvx.png
>
> are samples [0, 512] the positive frequencies and [513, 1024] the negative frequencies (in two-sided FFT).
> I.e. that to be correct the plot should actually look like [513, 1024] is [-512, 0] and [0,512] is [0,512], but is this the np.fft.fft way to return the negative frequencies (i.e in the latter half of the fft result)?

Yes, this is a standard convention used by many (most?) FFT implementations.


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