% ddom1 - a script that determines if the matrix A is diagonally dominant.
% If it isn't, then the matrix is modified so that it is diagonally dominant.
% See ddom2.m for an equivalent function.
%
% MATLAB Primer, 6th Edition
% Kermit Sigmon and Timothy A. Davis
% Section 7.2, page 35.

d = diag (A) ;
a = abs (d) ;
f = sum (abs (A), 2) - a ;
i = find (f >= a) ;
[m n] = size (A) ;
k = i + (i-1)*m ;
tol = 100 * eps ;
s = 2 * (d (i) >= 0) - 1 ;
A (k) = (1+tol) * s .* max (f (i), tol) ;