clear all;
A = [0.2 0.6 0; 0.2 0 0.2; 0.4 0.2 0.5]

eigA = eig(A)
detL = det(eye(3)-A)

invL = inv(eye(3)-A)

d = [100; 50; 200]
x = invL*d

d2 = [110; 100; 180];
Dd = d2-d
Dx = invL*Dd

A = [1 0 2 -1;
     1 0 -3 1;
     0 1 -1 1;
     0 1 0 -2]
b = [40; -5; 90; -2]
dA = det(A)

x = A \ b   % alternativamente x =inv(A)*b

N = 100;
X1 = 1 + 2*randn(N,1);
X2 = 2 + 2*randn(N,1);
eps = randn(N,1);
y  = 3 + 0.5*X1 +0.9*X2 + eps;

data = [y X1 X2];

dlmwrite('DatosMCO.txt',data);

clear all;
whos

impdata = importdata('DatosMCO.txt');
whos;

[N, K] = size(impdata);
y = impdata(:,1);
X1 = impdata(:,2);
X2 = impdata(:,3);

X = [ones(N,1) X1 X2];

beta = (X'*X)\(X'*y)   % alternativa beta = inv(X'*X)*(X'*y)

err = y - X*beta;
yhat = X*beta;

plot([y yhat]);
title('Ajuste')
legend('y','yhat');

plot(err);
title('Errores');