[Numpy-discussion] Functions for indexing into certain parts of an array (2d)

Robert Kern robert.kern at gmail.com
Sat Jun 6 03:09:47 EDT 2009

On Sat, Jun 6, 2009 at 02:01, Fernando Perez <fperez.net at gmail.com> wrote:
> Howdy,
> I'm finding myself often having to index *into* arrays to set values.
> As best I can see, in numpy functions/methods like diag or tri{u,l}
> provide for the extraction of values from arrays, but I haven't found
> their counterparts for generating the equivalent indices.
> Their implementations are actually quite trivial once you think of it,
> but I wonder if there's any benefit in having this type of machinery
> in numpy itself. I had to think of how to do it more than once, so I
> ended up writing up a few utilities for it.
> Below are my naive versions I have for internal use.  If there's any
> interest, I'm happy to document them to compliance as a patch.


diag_indices() can be made more efficient, but these are fine.

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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