[Numpy-discussion] Question about numpy.max(<complex matrix>)

Robert Kern robert.kern@gmail....
Fri Sep 21 14:02:52 CDT 2007


Stuart Brorson wrote:
> Hi guys,
> 
> As a NumPy newbie, I am still learning things about NumPy which I didn't
> expect.  Today I learned that for a matrix of complex numbers,
> numpy.max() returns the element with the largest *real* part, not the
> element with the largest *magnitude*.

There isn't a single, well-defined (partial) ordering of complex numbers. Both
the lexicographical ordering (numpy) and the magnitude (Matlab) are useful, but
the lexicographical ordering has the feature that

  (not (a < b)) and (not (b < a)) implies (a == b)

This is not the case for using the magnitude.

You can get the element of maximum magnitude like so:

  a.flat[absolute(a.flat).argmax()]

-- 
Robert Kern

"I have come to believe that the whole world is an enigma, a harmless enigma
 that is made terrible by our own mad attempt to interpret it as though it had
 an underlying truth."
  -- Umberto Eco


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