lm builds a statistical model. set.seed(555) x <- 1:20 A <- 15 B <- 0.4 E <- runif(length(x), -1, 1) * (2 + x/20) y <- A + B*x + E X11() plot(x, y, pch=16, col='blue') model <- lm(y~x) model abline(model, col='red' , lwd=3) abline(A, B , col='green', lwd=3) # wait for mouse click or enter pressed z <- locator(1)