[SciPy-Dev] Strange code in scipy.signal.decimate

[Paul Hobson]

If you make the changes and run the test suite, do the pertinent tests pass?
-Paul

On Thu, Oct 18, 2018 at 2:49 PM Daniele Nicolodi <daniele at grinta.net> wrote:

> On 18-10-2018 15:28, Paul Hobson wrote:
> > Dan,
> >
> > I might be missing something, but dlti returns a subclass of
> > LinearTimeInvariant. Point is, it's not a tuple, but a class with
> > multiple attributes and method. Simple tuple unpacking won't likely work
> > unless the authors of LinearTimeInvariant really went out of their way
> > to make it so.
>
> The point is not to go through the `dlti` class at all.
>
> Please look at the replacement code I posted: it works.
>
> Cheers,
> Dan
>
> > -Paul
> >
> > On Thu, Oct 18, 2018 at 1:58 PM Daniele Nicolodi <daniele at grinta.net
> > <mailto:daniele at grinta.net>> wrote:
> >
> >     Hello,
> >
> >     I was having a look at the scipy.signal.decimate() function and I
> >     noticed some strange looking code:
> >
> >         elif ftype == 'iir':
> >             if n is None:
> >                 n = 8
> >             system = dlti(*cheby1(n, 0.05, 0.8 / q))
> >             b, a = system.num, system.den
> >
> >     This is used to setup the anti aliasing low pass filter. What I don't
> >     understand is the dance to obtain the IIR numerator and denominator
> >     coefficients. Couldn't the above be simply as the code below?
> >
> >         elif ftype == 'iir':
> >             if n is None:
> >                 n = 8
> >             b, a = cheby1(n, 0.05, 0.8 / q)
> >
> >     Am I missing something?
> >
> >     Thanks!
> >
> >     Cheers,
> >     Dan
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> >
> >
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