To be clear, this: >> How can I get the output to show all 3 groups that I have inputted? There >> are only group 2 and group 3 on the output, group 1 is missing. Also there >> is a subgroup (subgroup 1) of the total 9 subgroups missing. I would like >> to see the p-value of the missing group and missing sub-group even though >> I'm sure they are not significantly different (>0.05).
shows a fundamental lack of understanding of the basic ideas of linear modeling (since it's basically nonsense -- an impossibility). You would do well to contact a local statistician to help you out. Cheers, Bert On Thu, Oct 14, 2010 at 12:50 PM, Joshua Wiley <jwiley.ps...@gmail.com> wrote: > Hi Robert, > > In R, the default treatment contrasts for factor class variables in > regression treats the first level as the reference group when creating > the contrast matrix for the regression, so it is not really a matter > of changing the formula. > > This might provide some insight: > http://www.ats.ucla.edu/stat/r/library/contrast_coding.htm > > There are many ways to handle categorical data, and without knowing > exactly what you want, it is difficult to give any sound suggestions. > It really depends on your question. > > > Cheers, > > Josh > > > On Thu, Oct 14, 2010 at 12:34 PM, Robert Quinn <rqu...@fbr.org> wrote: >> I have the following formula for a linear model: >> >> z <- lm(y~x + factor(a) + factor(b), data=NT2010) >> >> where a (groups) and b (Sub-groups) are categorical variables (factors), x >> is a continuous covariate, and y the response variable. Since b is nested >> within a, the formula can also be written as: >> >> z <- lm(y~x + factor(a) + factor(a)/factor(b), data=NT2010) >> >> and the same output is achieved when summary(z) is called. >> >> How can I get the output to show all 3 groups that I have inputted? There >> are only group 2 and group 3 on the output, group 1 is missing. Also there >> is a subgroup (subgroup 1) of the total 9 subgroups missing. I would like >> to see the p-value of the missing group and missing sub-group even though >> I'm sure they are not significantly different (>0.05). How do I change the >> original formula to get all groups and sub-groups outputted? > >> >> >> [[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. > > > -- > Joshua Wiley > Ph.D. Student, Health Psychology > ______________________________________________ > 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. > -- Bert Gunter Genentech Nonclinical Biostatistics 467-7374 http://devo.gene.com/groups/devo/depts/ncb/home.shtml ______________________________________________ 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.