Changing multiple elements (of known coordinates) of a matrix without a for loop

Question

I have a matrix say

Z = [1 2 3;
     4 5 6;
     7 8 9]

I have to change its values, say at positions (2,2) and (3,1), to some specified v

Answer 1

Use sub2ind with multiple entries for rows and columns

Z(sub2ind(size(Z), rowNos, colNos))=0

Example:

Z = [1 2 3;
    4 5 6;
    7 8 9];

rowNos = [2, 3];
colNos = [2, 1];

Z(sub2ind(size(Z), rowNos, colNos))=0

Z =

     1     2     3
     4     0     6
     0     8     9