[Numpy-discussion] method to calculate the magnitude squared

[Phillip Feldman]

The ufunc approach makes sense.

Something like abs2 is essential for anyone who does signal processing
simulations using NumPy.

Phillip

On Sat, Oct 10, 2015 at 11:29 AM, Nathaniel Smith <njs at pobox.com> wrote:

> On Oct 10, 2015 10:50 AM, "Charles R Harris" <charlesr.harris at gmail.com>
> wrote:
> >
> > On Sat, Oct 10, 2015 at 11:14 AM, Marten van Kerkwijk <
> m.h.vankerkwijk at gmail.com> wrote:
> >>
> >> > We tend to avoid adding methods. 2) would be a very easy enhancement,
> just a slight modification of sqr.
> >>
> >> Did you mean `np.square`? Sadly, that doesn't do the right thing:
> `np.square(1+1j)` yields `2j`, while one wants `c*c.conj()` and thus `2`.
> Or, for fastest speed, really just `c.real**2 + c.imag**2`.
> >
> >
> > Yes, I meant the new function could made by reusing the square code with
> slight modifications.
> >
> >>
> >> My guess would be that a new ufunc, say `np.abs2` or `np.modulus2` or
> so, would be more appropriate than defining a new method. I'd also be
> hesitant to define a new private method -- I like how those usually are
> just used to override python basics.
> >
> >
> > Julia uses abs2.
>
> I don't have an opinion on whether abs2 is important enough to bother with
> (I don't work much with complex numbers myself, nor have I run any
> benchmarks), but I agree that if we do want it then adding it as a regular
> ufunc would definitely be the right approach.
>
> -n
>
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