Re: no way for simple matrix lookup ?

[Jonathan C. Webster]

D. Goel wrote:
> Hi
>
> [1] Suppose A is a nxn matrix.  And b and  c are vectors.  How do i
> return elements of A specified by b and c? 
>
> i.e. Want to return a vector D, such that 
> D(i) = A(b(i), c(i)) 
Ravel the matrix A out into one long vector, A_vec, using fortran indexing if 
you want.
Then combine vec_b and vec_c into a single index vector into your A_vec.
 .
vec_3 = vec_b + size(A)(1) * (vec_c - 1)

Finally, your new reordered result vector D_vec

D_vec = A_vec(vec_3)

I think thats right, but check it. Think carefully about which should be vec_b 
and vec_c.

Jonathan Webster



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