matrices

[arbongard]

How would I write a subrountine that takes 2 parameters (a constant and a square matrix). Then adds that constant to the every element of the diagonal of the matrix, and passes the results back in a new parameter?

Then out puts the new matrix after the subtracted constant

I have the general idea but getting stuck on the diagonal part.

[Hutch_sas · Accepted solution]

A quick way to add a constant to the diagonal elements of a matrix:

/* add B to diagonal of a square matrix A */

C = A + diag(  j(nrow(A),  1,   B)  );