# [Numpy-discussion] Help w/ indexing, please

David Goldsmith d.l.goldsmith@gmail....
Tue Jul 27 13:19:39 CDT 2010

```On Tue, Jul 27, 2010 at 9:32 AM, John Salvatier
<jsalvati@u.washington.edu>wrote:

> I am pretty sure you should be able to do
>
> R = C[L, :]  and get the array you want.
>
> Try it with a small matrix where  you know the result you want. You may
> need to transpose some axes afterwards, but I don't think you should.
>

Thanks, John, that works; you may be right about the transposing, but I can
work that out empirically.  Thanks again!

DG

>
> On Tue, Jul 27, 2010 at 9:10 AM, David Goldsmith <d.l.goldsmith@gmail.com>wrote:
>
>> Hi!  I have a large M x K, M, K ~ 1e3 array L of indices - non-negative
>> integers in the range 0 to N-1 - and an N x 3 array C (a matplotlib
>> colormap).  I need to create an M x K x 3 array R such that R[m,k,j] =
>> C[L[m,k], j], j = 0,1,2.  I want to do so w/out having to loop through all
>> the (m,k) index pairs, but I'm having trouble wrapping my brain around how
>>
>> DG
>>
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>>
>
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