Dear Help-list, I have solved the problem by simply deleting the erroneous
"0" in the "CR core - CR EC" contrast and deleting the
unnecessary command "test=adjusted(summarytype =
"single-step")". Regards,B. Jessop
> From: deelman@hotmail.com> To: r-help@r-project.org
> Date: Sun, 17 Jul 2011 21:04:51 -0300
> Subject: [R] Multiple comparison test on selected contrasts
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> Dear Help-list, How can I do a multiple comparison test (mct) on selected
contrasts from a linear model while using packages lme4 and multcomp? I am
running R 2.13.0 under Windows 7. The following linear model and mct produces a
global mct of 15 paired contrasts of the combined (Site, Position) factor
SitePos of which only 9 are of interest. Model.G = lmer(log10(SrCa) ~ SitePos +
(1 | Eel), data = Data1)
> Model.G.mct = glht(Model.G, linfct = mcp(SitePos =
"Tukey"))summary (Model.G.mct) The following code creates the desired
reduced set of contrasts but I have been unable to apply it correctly to the
mct. contr = rbind("CR core - MH core" = c(1,0,0,-1,0,0),"CR
core - CR edge" = c(1,0,-1,0,0,0),
> "CR core - CR EC" = c(1,-1,0,0,0,0,0),"CR edge - MH
edge" = c(0,0,1,0,0,-1),
> "CR edge - CR EC" = c(0,-1,1,0,0,0),"CR EC - MH EC" =
c(0,1,0,0,-1,0),
> "MH core - MH edge" = c(0,0,0,1,0,-1),"MH core - MH EC"
= c(0,0,0,1,-1,0),
> "MH edge - MH EC" = c(0,0,0,0,-1,1)) Execution of this code
produces the error message: In rbind ('CR core - MH core" =
c(1,0,0,-1,0,0), etc.: number of columns of results is not a multiple of vector
length (arg 1)'.
> Model.G.mct2 = glht(Model.G, linfct = mcp(SitePos = contr)) #execution
produces "Error in linfct{[nm]} %*% c: non-comformable argument", as a
consequence of the previous error
> summary (Model.G.mct2, test = adjusted(summarytype =
"single-step")) Clearly, this approach is incorrect (and I have tried
others). How can I introduce the selected set of contrasts into the mct?
Thanks for any help provided. Regards,B. Jessop
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