Hi all,

I've posted this question before, but did not get any reply. I post it
again here and see if anybody can help. Thank you.

I have a nested model with the following effects
    fixed: treatments
    random: experiment_date

I used lme() to model the data
mod1 <- lme(N_cells ~treatments-1, random=~1|experiment_date, method='ML')

Then I want to compare all the other treatments to the control (included in the
"treatments" in mod1). After a fair amount of searching around, I decided
to use glht() from the multcomp package (any other suggestions?).
lvl.treatments=table(treatments)
K = contrMat(lvl.treatments,type='Dunnett',base=1)
mc<-glht(mod1, linfct=mcp(treatments=K),alternative='greater')

But I got the following error:
Error in contr.treatment(n = 0L) :
  not enough degrees of freedom to define contrasts

I tried to extract the df parameter using "modelparm()", but the
function couldn't
be applied to lme:
Error in UseMethod("modelparm") :
  no applicable method for 'modelparm' applied to an object of class "lme"

The degree of freedom of the fixed effect was 194. I tried to specify
the number
in glht, but got the same error as "not enough degrees of freedom to define
contrasts".

Does anyone know what's happening and how I could possibly solve the problem?
Thank you so much.

Best,
Wendy

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