Find multiple row and column combinations in a matrix in Matlab

Question

I have the following matrix:

>> MatrixA = [1 2 3 4; 5 6 7 8; 9 10 11 12; 13 14 15 16]
MatrixA =
     1     2     3     4
     5     6     7     8
     9    10    11    12
    13    14    15    16

I want to find the following:

• for row 1, I want the 2nd column
• for row 2, I want the 3rd column
• for row 3, I want the 4th column
• for row 4, I want the 4th column

Currently I accomplish this with the following line:

>>diag(MatrixA([1 2 3 4], [2 3 4 4]))
ans =
     2
     7
    12
    16

Is there a more direct way to do this (without using diag)?

Answer 1

Well you could use sub2ind, it might be more intuitive. I don't think there is much benefit though, maybe it's more readable:

ind = sub2ind(size(MatrixA), [1 2 3 4], [2 3 4 4])
MatrixA(ind)