lmer and post-hoc testing

-----Oorspronkelijk bericht-----
Van: r-sig-mixed-models-bounces at r-project.org 
[mailto:r-sig-mixed-models-bounces at r-project.org] Namens 
SHONA MARY LESLIE
Verzonden: maandag 10 januari 2011 17:54
Aan: r-sig-mixed-models at r-project.org
Onderwerp: [R-sig-ME] lmer and post-hoc testing

Hi there,

I am investigating habitat preference in 9-spined 
sticklebacks using 4 experimental arenas (each fish spent 
same time in each arena) and want to know whether the time in 
the shallow area was different between arenas.

I carried out a generalised linear mixed model (using lmer), 
putting in the fish ID as a random effect, and the 
distribution as binomial (since it's proportion data); as follows...

model1<-lmer(y~factor(Arena)+SL+(1|FishID), family=binomial)
summary(model1)

This worked but I can't work out how to run a Tukey test, to 
see which arenas were different.  I have tried... (with error 
message underneath)

TukeyHSD(model1)

Error in UseMethod("TukeyHSD") : 
  no applicable method for 'TukeyHSD' applied to an object of 
class "mer"

summary(glht(model1,linfct=mcp(Arena="Tukey")))

Error in summary(glht(model1, linfct = mcp(Arena = "Tukey"))) : 
  error in evaluating the argument 'object' in selecting a 
method for function 'summary'

glht(model1, linfct=mcp(Arena="Tukey"))

Error in mcp2matrix(model, linfct = linfct) : 
  Variable(s) 'Arena' have been specified in 'linfct' but 
cannot be found in 'model'! 

glht(model1, linfct=mcp(factor(Arena)="Tukey")

Error: unexpected '=' in "glht(model1, linfct=mcp(factor(Arena)="

I have read some of the R help archives and it has been 
pointed out that Tukey may or may not work with lmer (I 
downloaded the newest version and still no luck).  Any ideas? 
 If Tukey won't work, are there others that might?

Thanks,
Shona