Dear readers, I have a very basic question about the usage of the lm() function. Sorry if I should have read this somewhere, but I was not able to find my answers in the accompanied documentation and r-project website. Suppose I have an interaction term Num1 : Num2 somewhere in my formula, where both Num1 and Num2 are numeric (not factors). Should I now center Num1 and Num2 myself first, or is this done somewhere internally? Num1 <- Num1 - mean(Num1) ps> I might be doing something strange. I analyzed different models, both containing a covariate (say, C1 and C2, which both are numeric), and now I was trying to see what happens if I use a single model including both covariates. And there I arrived at the above situation where I was also experimenting with a model containing C1:C2 (could very well be i'm already breaking assumptions when there actually is any interaction between covariates, but i'm just trying several things as I'm quite a newbie in the world of statistics). Thanks for your time, Dan.
______________________________________________ R-help@r-project.org mailing list 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.
