Regresión

n = 100;
x1 =  1:n;
x2 = round(runif(n,0,1),2);
x3 = round(rnorm(n),2);
x4 = round(runif(n,10,20),2);
x5 = 0.2*x1+0.7*x2+0.1*x4;
er = round(rnorm(n,0,2),2);

y = 10+0.8*x1 -12*x2 + 6 *x3 + er;

par(mfrow=c(1,3));
plot(x1,y);
plot(x2,y);
plot(x3,y);

X=cbind(1,x1,x2,x3);
bet=round(solve(t(X) %*% X) %*% t(X) %*% y,2);
ya=X%*%bet;
ee=y-ya;
s2 = t(ee)%*% ee/(n-3-1);

dat=cbind(y,x1,x2,x3);
cor(dat);

reg1 = lm(y~x1 + x2 +x3 + x4 + x5);
summary(reg1);