How to add sparse matrix to an n*n matrix

Let say;

A = ones(4,4);

i = [2 4]; j = [1,3];

B = sparse(i,j,[9 9]);

A + B;

How can I add A+B, so that the component A(2,1) = 1+9 and A(4,3) = 1+9. Rest of the components of matrix A should be 1. I am trying the above snippet but it outputs error: Error using +

Please help me if its possible to add accordingly, Thanks.

Answer 1

[KSSV]

To add A and B, they should be of same dimension. In your case A is 4x4 matrix whereas B is not. So to add them, you have to make B to the same size of A.

A = ones(4,4);
i = [2 4]; j = [1,3];
B = sparse(i,j,[9 9],4,4) ;
iwant = A + B

iwant = 4×4

1 1 1 1 10 1 1 1 1 1 1 1 1 1 10 1

[SALMAN KHAN]

Thanks. It helps me alot.