In addition to David's great answer also read ?contr.SAS ?contr.treatment ?relevel
and also sections 4 and 11.1.1 in An Introduction to R. On Fri, May 3, 2013 at 9:47 PM, David Winsemius <dwinsem...@comcast.net>wrote: > > On May 3, 2013, at 3:32 PM, Iuri Gavronski wrote: > > > Hi, > > I would like to know the criteria by which R removes a factor in linear > > models. For example, I have a four level factor, and R creates 3 dummies > to > > estimate coefficients. Which level is chosen? Can I chance it? > > The default order is alphabetical. Lowest lexical sorted item is the > reference level. > > Changing levels is possible: > > ?levels > ?factor > > -- > David Winsemius > Alameda, CA, USA > > ______________________________________________ > 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. > -- Gregory (Greg) L. Snow Ph.D. 538...@gmail.com [[alternative HTML version deleted]] ______________________________________________ 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.
