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

[Warren Weckesser]

On Thu, Aug 31, 2017 at 2:41 PM, Phillip Feldman <
phillip.m.feldman at gmail.com> wrote:

> This is an excellent change!
>
>

Thanks Phillip.


What does the code do if the caller specifies both `fs` and `nyq`?
>
>

It raises an exception: ValueError("Values cannot be given for both 'nyq'
and 'fs'.")

Warren


On Wed, Aug 30, 2017 at 10:22 PM, Warren Weckesser <
> warren.weckesser at gmail.com> 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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>
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