Re: no way for simple matrix lookup ?

[Etienne Grossmann]

 A = reshape (1:60,3,5,4);
                      
 b = ones(5,1)*[2 3 1 2 3 1];          # Quintiplate all indexes
 c = ones(5,1)*[4 1 2 3 4 1];          # idem
 d = [1:5]'*ones(1,6);                 # Run indexes 
 D = A(sub2ind (size (A),b, d, c))

  Seems correct



On Wed, Jun 16, 2004 at 03:08:22PM -0400, D. Goel wrote:
# 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?
# 
# 
# 
# 

-- 
Etienne Grossmann ------ http://www.cs.uky.edu/~etienne