Add numpy.phase in addition to numpy.angle

I wanted to suggest adding a function which directly gives the phase of a complex valued number instead of the angle:

def phase(z): # Calculates the phase of a complex number
  r = numpy.absolute(z)
  return (z.real/r + 1j * z.imag/r)

This is a simple enhancement, which I think would make numpy more consistent and offer the benefit of simply being faster in large loops, rather than going the ang = numpy.angle(z); phase = numpy.cos(ang) + 1j * numpy.sin(ang) route (or numpy.cos(1j * ang), for what it’s worth).

[njsmith]

Yeah, if my guess is right and no-one uses that, then no-one will complain if we transition it… it’d take a few releases still to follow the deprecation cycle but it might be best to ask people to just write ‘z / np.abs(z)’ until 1.11 or whatever, rather than add a new function to the namespace?

On Thu, Aug 15, 2013 at 9:48 PM, Charles Harris [e-mail]:

Yep, that is what it does 😉 I don’t know that we can just change it, OTOH, I doubt many use the current form for complex.

— Reply to this email directly or view it on GitHubhttps://github.com/numpy/numpy/issues/3621#issuecomment-22729122 .

[njsmith]

I don’t have a strong opinion either way, just raising the issue. Having a plethora of confusingly similar functions should be avoided though…

what the heck does our sign function do for complex numbers? Is this like cmp(z, 0) with lexicographic order? Is that actually useful to anyone and could we change it to this much more sensible definition?

(numpy.linalg.slogdet is one function that uses the abs(z) == 1 definition of sign for complex numbers.)

On Thu, Aug 15, 2013 at 2:38 PM, Charles Harris [e-mail]:

@njsmith https://github.com/njsmith Some folks use that as the signfunction for complex, so it might be worth having.

— Reply to this email directly or view it on GitHubhttps://github.com/numpy/numpy/issues/3621#issuecomment-22703179 .