[Numpy-discussion] sum of two arrays with different shape?
Robert Kern
robert.kern at gmail.com
Sun Dec 17 20:39:30 CST 2006
zhang yunfeng wrote:
> Hi, I'm newbie to Numpy.
>
> When reading tutorials at
> http://www.scipy.org/Tentative_NumPy_Tutorial
> <http://www.scipy.org/Tentative_NumPy_Tutorial>, I found a snippet about
> addition of two arrays with different shape, Does it make sense? If
> array shapes are not same, why it doesn't throw out an error?
When two arrays of different shapes are operated against each other, numpy tries
to "broadcast" them to a compatible shape according to certain rules. This is a
fairly powerful concept, and it provides quite a lot of convenience. The
following wiki page has an explanation of the broadcasting rules:
http://www.scipy.org/EricsBroadcastingDoc
It still refers to Numeric, numpy's predecessor, but the concepts still apply
(change "Numeric" to "numpy" and "NewAxis" to "newaxis", and I believe all of
the code examples will be correct).
--
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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