[SciPy-Dev] Proposed API change for some functions in scipy.signal

[Gael Varoquaux]

Hi Warren,

Good to see that you are working on improving scipy.signal API. I have
not strong opinion on the changes that you propose. I am really not an
expert in DSP. I do find scipy.signal difficult to work with.

While we are at it: is there a reason that scipy.signal.spline_filter
only support 2D arrays? I naively thought that it would be good
functionality to have on 1D signals.

Gaël

On Thu, Aug 31, 2017 at 01:22:26AM -0400, Warren Weckesser wrote:
> I've been using quite a few of the functions in scipy.signal recently, and I've
> been reminded of some of the quirks of the API. I have submitted a pull request
> to clean up one of those quirks.

> In the new pull request, I have added the argument 'fs' (the sampling
> frequency) to the following functions:  firwin, firwin2, firls, and remez.  For
> firwin, firwin2 and firls, the new argument replaces 'nyq', and for remez, it
> replaces 'Hz'.  This makes these functions consistent with the other functions
> in which the sampling frequency is specified using 'fs': periodogram, welch,
> csd, coherence, spectrogram, stft, and istft. 'fs', or in LaTeX, $f_s$, is
> common notation for the sampling frequency in the DSP literature.

> In the pull request, the old argument is given a "soft" deprecation. That means
> the docstring says the argument is deprecated, but code to actually generate a
> DeprecationWarning has not been added yet.  I'm fine with adding that now, but
> some might prefer a relatively long and soft transition for these changes. 
> (Personally, I don't mind if they hang around for a while, but they should be
> gone by 2.0. :)

> I haven't changed the default value of the sampling frequency.  For the FIR
> filter design functions firls, firwin and firwin2, the default is nyq=1.0
> (equivalent to fs=2), while for remez the default is Hz=1 (i.e. fs=1).  The
> functions that currently already use 'fs' all have the default fs=1. Changing
> the default for the FIR design functions would be a much more disruptive
> change.

> Comments here or on the pull request are welcome.

> P.S. I can see future pull requests in which 'fs' is added to functions that
> currently don't have an argument to specify the sampling frequency.  I'm
> looking at you, freqz.


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-- 
    Gael Varoquaux
    Researcher, INRIA Parietal
    NeuroSpin/CEA Saclay , Bat 145, 91191 Gif-sur-Yvette France
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