[Numpy-discussion] numpy-izing a loop

[Stéfan van der Walt]

Hi Paul

2009/2/10 Paul Rudin <paul at rudin.co.uk>:
>
> I've just written this snippet of code:
>
> result = numpy.empty((dim, dim, dim), numpy.bool)
> for x in xrange(dim):
>    for y in xrange(dim):
>        for z in xrange(dim):
>            result[x, y, z] = ((xnear[y, z] < xfar[y, z]) and
>                               (ynear[x, z] < yfar[x, z]) and
>                               (znear[x, y] < zfar[x, y]))
>
>
> Is there a way to get numpy to do the looping?

You can try the following:

x = np.arange(dim)
y = np.arange(dim)
z = np.arange(dim)

result = (xnear[y,z] < xfar[y, z]) & (ynear[x, z] < yfar[x, z]) &
(znear[x,y] < zfar[x,y])

It broadcasts correctly, but you'll have to verify the results to be sure.

Cheers
Stéfan