Please, do not post if you do not know the answer. People will see this has answers and skip.
I tried with mat1=contrasts(fixw$snconv) mat1=mat1[,-2] summary(frm2sum <- glm(resp.frm ~ C(snconv,contr=mat1)+mprime+mshape,data=fixw,family="quasibinomial")) the unwanted level is still there. Unbelievable. Stephen Bond -----Original Message----- From: David Winsemius [mailto:dwinsem...@comcast.net] Sent: Wednesday, July 07, 2010 4:15 PM To: Bond, Stephen Cc: r-help@r-project.org Subject: Re: [R] forcing a zero level in contr.sum On Jul 7, 2010, at 4:04 PM, Bond, Stephen wrote: > Clarifying my question: > > options(contrasts = c("contr.sum", "contr.poly")) >> contrasts() > [,1] [,2] [,3] [,4] [,5] > 01 1 0 0 0 0 > 03 0 1 0 0 0 > 05 0 0 1 0 0 > 06 0 0 0 1 0 > 07 0 0 0 0 1 > 09 -1 -1 -1 -1 -1 > > I need to force the coefficient on level 03 to be zero. ?factor ?relevel Perhaps worth a try: fixw$snconv <- relevel(fixw$snconv, ref="03") (But I wonder if using contr.sum will ever generally satisfy that goal, since contr.sum calculates the difference from a grand mean and this will only work if a) the GM=0 and b) there is only one term on the RHS of the model, and c) probably a bunch of other restrictions.) -- David. > > Thank you. > > Stephen Bond > -----Original Message----- > From: David Winsemius [mailto:dwinsem...@comcast.net] > Sent: Wednesday, July 07, 2010 3:44 PM > To: Bond, Stephen > Cc: r-help@r-project.org > Subject: Re: [R] forcing a zero level in contr.sum > > > On Jul 7, 2010, at 3:13 PM, Bond, Stephen wrote: > >> I need to use contr.sum and observe that some levels are not >> statistically different from the overall mean of zero. >> What is the proper way of forcing the zero estimate? It seems the >> column corresponding to that level should become a column of zeros. >> Is there a way to achieve that without me constructing the design >> matrix? >> Thank you. > > lm( formula = z ~ x + y + 0, ...) _might_ do something close to > what you want. > > > > > David Winsemius, MD > West Hartford, CT > David Winsemius, MD West Hartford, CT ______________________________________________ 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.
