On Mon, 10 Feb 2003, Luca Scrucca wrote: > I found a strange behaviour in the lqs function.
Why is this strange? It *is* covered in the Note on the help page: please read it and the reference there. > Suppose I have the following data: [...] > Now, instead of using the formula, I want to provide the design matrix and > the response, then: > > X <- cbind(1, x1, x2) > mod2 <- lqs.default(X, y, intercept=F, method="lms", nsamp="exact") > mod2$coefficients > x1 x2 > 35.4217275 0.4276641 -1.2834731 > mod2$bestone > [1] 6 14 15 > > The results are not the same (?!). Furthermore, if I create the design > matrix without the column of 1's for the intercept: Right, it's not the same algorithm. > X <- cbind(x1, x2) > mod3 <- lqs.default(X, y, intercept=T, method="lms", nsamp="exact") > I get the same result I had using the formula (see mod1). > This is confusing me! That *is* the same algorithm. > Another small problem appears if I re-fit the first model using the > formula and asking to return the x-matrix and the response: > > lqs(y ~ x1 + x2, method="lms", nsamp="exact", x.ret=T, y.ret=T) > > Error in model.frame(formula, rownames, variables, varnames, extras, > extranames, : > variable lengths differ > > Does anyone know what's going on? No, but R has debugging tools for you to find out .... -- Brian D. Ripley, [EMAIL PROTECTED] Professor of Applied Statistics, http://www.stats.ox.ac.uk/~ripley/ University of Oxford, Tel: +44 1865 272861 (self) 1 South Parks Road, +44 1865 272866 (PA) Oxford OX1 3TG, UK Fax: +44 1865 272595 ______________________________________________ [EMAIL PROTECTED] mailing list http://www.stat.math.ethz.ch/mailman/listinfo/r-help
