On Sun, Jan 15, 2012 at 6:54 AM, David Cournapeau <cournape@gmail.com> wrote:

On Sat, Jan 14, 2012 at 11:53 PM, Nathan Faggian
<nathan.faggian@gmail.com> wrote:
> Hi,
>
> I am finding it less than useful to have the negative index wrapping on nd-arrays. Here is a short example:
>
> import numpy as np
> a = np.zeros((3, 3))
> a[:,2] = 1000
> print a[0,-1]
> print a[0,-1]
> print a[-1,-1]
>
> In all cases 1000 is printed out.
>
> What I am after is a way to say "please don't wrap around" and have negative indices behave in a way I choose. I know this is a standard thing - but is there a way to override that behaviour that doesn't involve cython or rolling my own resampler?

Although it could be possible with lots of work, it would most likely
be a bad idea. You will need to wrap something around your
model/data/etc... Could you explain a bit more what you have in mind ?

David

Another approach that might be useful, depending on the needs, is to use `np.ravel_multi_index()`, in which ndim coords can be passed in and flatten coords are returned. It has options of 'raise', 'wrap' and 'clip' for handling out-of-bounds indices. It wouldn't be built directly into the arrays, but if that isn't needed, this might work.

Ben Root