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Today's Topics:

   1. Re: signal.spectrogram doesn't change nperseg to length of
      window? (Eric Larson)


----------------------------------------------------------------------

Message: 1
Date: Mon, 21 Nov 2016 16:15:19 -0500
From: Eric Larson <larson.eric.d@gmail.com>
To: SciPy Developers List <scipy-dev@scipy.org>
Subject: Re: [SciPy-Dev] signal.spectrogram doesn't change nperseg to
        length of window?
Message-ID:
        <CAGu2niVW-MWH4h9Hk+tP7dssDv9YJ6JhJrQOvei8NrRxHQoKHQ@mail.gmail.com>
Content-Type: text/plain; charset="utf-8"

It looks like you are reading the docs correctly. From looking at the code,
I can confirm that it doesn't change `nperseg` based on what is passed for
`window`. So it looks like a bug to me.

Do you have time to look into making a Pull Request to fix it?

Eric


On Sat, Nov 19, 2016 at 10:41 PM, David Nicholson <nicholdav@gmail.com>
wrote:

> Hi scipy-dev list,
>
> I'm using spectrogram from scipy.signal with a custom window. My
> understanding from the docs is that when I provide an array_like for the
> window, the value for nperseg will change from the default of 256 to
> whatever the length is of the window I provide.
>
> But instead I get an error saying  'noverlap must be less than nperseg' and
> when I check with pdb I can see that nperseg is still the default value.
> I'm using a value for noverlap that's larger than the default nperseg, but
> less than the length of the window. I don't get the error if I call the
> function with 'nperseg=window.shape[0]'.
>
>  I skimmed the source and don't see anything in the _spect_helper function
> that would change nperseg to the length of window.
>
> Am I misunderstanding the docs, or am I calling the function wrong, or is
> this a bug?
>
> Here's my code:
> from scipy.io import wavfile
> from scipy.signal import slepian # i.e. 'DPSS' window used for FFT
> from scipy.signal import spectrogram
>
> FFT_SIZE = 512
> FFT_OVERLAP = FFT_SIZE - 32
> win_dpss = slepian(FFT_SIZE, 4/FFT_SIZE) #shape =
>
> [rate,data] = wavfile.read('a_file_you_have.wav')
> f,t,spec = spectrogram(data, rate, window=win_dpss, noverlap=FFT_OVERLAP)
>
> Thanks for your help
> --David
>
> --
> David Nicholson, Ph.D. Candidate
> Sober Lab <http://www.biology.emory.edu/research/Sober/Home.html>, Emory
> Neuroscience Program. <http://www.emory.edu/NEUROSCIENCE/>
> www.nicholdav.info; <http://www.nicholdav.info>
> https://github.com/NickleDave
>
> _______________________________________________
> SciPy-Dev mailing list
> SciPy-Dev@scipy.org
> https://mail.scipy.org/mailman/listinfo/scipy-dev
>
>
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