N <- 5 x1 <- c( 3.1, 1.2, -3.3, 2.7, -1.8 ) x2 <- c( -4.2, 3.1, 1.0, -4.0, -2.1 ) y <- c( -1.2, 4.3, -2.5, -2.0, -4.3 )