[R-sig-ME] Contrast in lme4

[Ben Bolker]

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  "How do I set up custom contrasts?" is (1) not specific to mixed
models (so not really appropriate for this list -- maybe try r-help or
Stack Overflow); (2) rather tricky in R (it may be difficult in all
statistics packages/languages, I don't know); and (3) sufficiently
detailed that the information you give below isn't really quite
sufficient.  A reproducible example will help when you post your
question somewhere else.  You can use the "contrast" package, or the
"multicomp" package, to test contrasts.  As far as how the contrasts
are set up, there's a reasonable description in Crawley's _Data
Analysis in S-PLUS_ book, or see

http://www.ats.ucla.edu/stat/r/library/contrast_coding.htm
http://ms.mcmaster.ca/~bolker/classes/s4c03/notes/week2B.pdf


On 15-03-12 01:52 PM, Douglas Bates wrote:
> It is better to send questions like this to the 
> R-SIG-Mixed-Models at R-project.org mailing list, which I am cc:ing on
> this reply.
> 
> On Thu, Mar 12, 2015 at 3:09 AM adeela uaf <adeela.uaf at gmail.com>
> wrote:
> 
>> Dear Douglas Bates, How to perform contrast analysis for fixed
>> effects in lme4 package. My data is same as sleepstudy data with
>> an additional cloumn comprising  12 treatments also. The
>> structure of the treatmnets is such that: 1) 1 treatment is
>> control 2) 4 treatments are bio-agents. 3) 3 treatments are
>> botanical. 4) 2 are bi prodcts 5) 2 are fungisides I want to make
>> comparison among the groups which differ significantly after 
>> Model<-lmer(Disease~Trt+Date+Trt*Date+(1|Subject),data=YR) Best
>> Regars, Adeela
>> 
> 
> [[alternative HTML version deleted]]
> 
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