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Re: no way for simple matrix lookup ?
From: |
D. Goel |
Subject: |
Re: no way for simple matrix lookup ? |
Date: |
Wed, 16 Jun 2004 15:08:22 -0400 |
User-agent: |
Gnus/5.1002 (Gnus v5.10.2) Emacs/21.2 (gnu/linux) |
Etienne Grossmann <address@hidden> writes:
> A = reshape (1:12, 3,4);
>
> b = [2 3 1 2 3];
> c = [4 1 2 3 4];
>
> D = A(sub2ind (size (A),b, c))
>
> D = diag (A(b,c)) # Don't do that
>
Many thanks to Etienne for the above solution, and to everyone else
for similar solutions. Anyone have any ideas on the question below
(which is the actual problem at hand) -->
> #
> # [3] More generally, the problem i am struggling with is:
> #
> # A is a nxmxl matrix. b and c are vectors.
> # I am looking for a vector D, such that D(i,:)= A(b(i), :, c(i)).
> #
> # Any way to do that?