Thank you for your replies! I am terribly sorry for the code not being reproducible, is the first time I am posting here, I run the code several times before I posted, but...I forgot about the library used.
To answer to your questions: How do you know this answer is "correct"? What I am doing is actually a "fixed effect" estimation. I apply a projection matrix to the data, both dependent and independent variables, projection which renders the regressors that do not vary, equal to basically zero - the x1 from the post. Once I apply the projection, I need to run OLS to get the estimates, so x1 should be zero. Therefore, the results with the scaled regressor is not correct. Besides, I do not see why the bOLS is wrong, since is the formula of the OLS estimator from any Econometrics book. Here again the corrected code: install.packages("corpcor") library(corpcor) n_obs <- 1000 y <- rnorm(n_obs, 10,2.89) x1 <- rnorm(n_obs, 0.00000000000001235657,0.000000000000000045) x2 <- rnorm(n_obs, 10,3.21) X <- cbind(x1,x2) bFE <- lm(y ~ x1 + x2) bFE bOLS <- pseudoinverse(t(X) %*% X) %*% t(X) %*% y bOLS Best, Raluca Gui -- View this message in context: http://r.789695.n4.nabble.com/Error-in-lm-with-very-small-close-to-zero-regressor-tp4705185p4705212.html Sent from the R help mailing list archive at Nabble.com. ______________________________________________ R-help@r-project.org mailing list -- To UNSUBSCRIBE and more, see https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide http://www.R-project.org/posting-guide.html and provide commented, minimal, self-contained, reproducible code.