[Numpy-discussion] Getting an array's indices when a given condition is true

Robert Kern robert.kern@gmail....
Sat Oct 18 22:13:16 CDT 2008


On Sat, Oct 18, 2008 at 22:00, Lane Brooks <lbrooks@mit.edu> wrote:
> If you want the indexes, check out the np.where command, e.g.
>
> idx = np.where(dat <= limit)

It's worth noting that where() confusingly has two modes of
functionality. This particular bit of functionality is also exposed
under the better-named nonzero() function. I prefer to use nonzero()
for this, and only use where() for its where(condition, value_if_true,
value_if_false) functionality.

-- 
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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