[Numpy-discussion] element wise help

[Chris Colbert]

unfortunately, the actual function being processes is not so simple, and
involves evaluating user functions input from the prompt as strings. So i
have no idea how to do it in Cython.

Let me look into this broadcasting.

Thanks Josef!

On Thu, May 7, 2009 at 12:56 PM, <josef.pktd at gmail.com> wrote:

> On Thu, May 7, 2009 at 12:39 PM, Chris Colbert <sccolbert at gmail.com>
> wrote:
> > suppose i have two arrays:  n and t, both are 1-D arrays.
> >
> > for each value in t, I need to use it to perform an element wise scalar
> > operation on every value in n and then sum the results into a single
> scalar
> > to be stored in the output array.
> >
> > Is there any way to do this without the for loop like below:
> >
> > for val in t_array:
> >
> >           out = (n / val).sum()  # not the actual function being done,
> but
> > you get the idea
> >
>
>
> broad casting should work, e.g.
>
> (n[:,np.newaxis] / val[np.newaxis,:]).sum()
>
> but it constructs the full product array, which is memory intensive
> for a reduce operation, if the 1d arrays are large.
>
> another candidate for a cython loop if the arrays are large?
>
> Josef
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