[Numpy-discussion] indexed arrays ignoring duplicates

Robert Kern robert.kern@gmail....
Wed Sep 29 12:28:10 CDT 2010


On Wed, Sep 29, 2010 at 12:00, Pauli Virtanen <pav@iki.fi> wrote:
> Wed, 29 Sep 2010 11:15:08 -0500, Robert Kern wrote:
> [clip: inplace addition with duplicates]
>> Use numpy.bincount() instead.
>
> It might be worthwhile to add a separate helper function for this
> purpose. Bincount makes a copy that could be avoided, and it is difficult
> to find if you don't know about this trick.

I'm fairly certain that most of the arrays used are fairly small, as
such things are reckoned. I'm not sure that in-place modification
would win us much. And I'm not sure what other name for the function
would make it easier to find. AFAICT, using bincount() this way is not
really a "trick"; it's just the right way to do exactly this job. If
anything, "x.fill(0);x[i] += 1" is the "trick".

-- 
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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