function B = ddom2 (A)
% B = ddom2 (A) returns a diagonally
% dominant matrix B by modifying the
% diagonal of A.
%
% MATLAB Primer, 6th Edition
% Kermit Sigmon and Timothy A. Davis
% Section 7.3, page 36.

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) ;

B = A ;