% Gauss-Seidel (Ejemplo 2.6.1)
clear
clc

A = [3 -1 0 -1; 1 -4 1 1; 0 -1 3 -1; -2 0 -1 4];
b = [-3; 0; 3; 11];


D = diag(diag(A));
E = -tril(A,-1);
F = -triu(A,1);

k = 0;
x = 0*b;
diff = inf;

Q = (D-E) \ F;
r =  (D-E) \ b;


while diff > 1e-3 && k < 100
    vec = Q*x + r;
    diff = norm(x-vec)
    x = vec
    k = k+1;

    pause
end