Deleting an irregular "row"/"column" from 2-d array

I have a 2d array, and I want to eliminate the same number of elements in each row (or column) (e.g. 1 element), but the index of that element is itself av vector. This operation would be relevant for doing seam-carving (content-aware image resize).

Is there any neat way of doing this without my array collapsing into a 1d vector?

A = (1:3)'*(1:3);
A =

     1     2     3
     2     4     6
     3     6     9
b = [1; 2; 2];
for r=(1:3)
    tmp = A(r,:);
    tmp(b(r)) = [];
    Y(r,:) = tmp;
end
Y =

     2     3
     2     6
     3     9

I seem to have a working method, but it is kind of cumbersome as I have to (?) make sure that the linear indexing into Y is strictly monotonic:

Y = A';
Y(sub2ind(size(A'), b, (1:3)')) = [];
Y = reshape(Y, size(A,2)-1, size(A,1))'

Anything neater?

Answer 1

[Matt J]

I think your solution is probably the best, except that I would avoid the extra calls to size() and ctranspose(). The latter are particularly expensive.

Y = A.';
[m,n]=size(Y);
Y(  sub2ind([m,n], b, (1:3))  )=[];
Y = reshape(Y, m-1, n).'