Hi!

Something funny happens to me in lnme. I don't know if it's a bug or not.
Here's a short sketch of the problem (you could skip the introduction and
just go to the models):

I'm counting the number of spider webs ( = response variable) along two
rivers, with a two-level treatment: free-flowing and dammed.
There are three field sites (random factor) along each river, and
measurements are done six times (= random factor for repeated measurements).

Webs are counted on four different distances along the river (fixed effect),
with six plots at each distance.

My model looks like this:

*
Model<-lme(Webslog1~Treatment*Distance,random=~Week|Uniquesite/Uniqueplot,method="REML")
*

I want to leave out the interaction between Treatment and Distance, so that
would go like this:
*
>ModelNoInteraction<-lme(Webslog1~Treatment+Distance,random=~Week|Uniquesite/Uniqueplot,method="REML")
*

However, then i get the error message:*
"Error in model.frame.default(formula = ~Week + Webslog1 + Treatment +  :
  invalid type (list) for variable 'Distance' "*

I first thought that it is for some reason just not allowed to leave out the
interaction. But when i try to run the first model again, i get the same
error message! Therefore i thought the thing could be a bug. The whole thing
looks like this:

*>
Model<-lme(Webslog1~Treatment*Distance,random=~Week|Uniquesite/Uniqueplot,method="REML")

>
ModelNoInteraction<-lme(Webslog1~Treatment+Distance,random=~Week|Uniquesite/Uniqueplot,method="REML")

Error in model.frame.default(formula = ~Week + Webslog1 + Treatment +  :
  invalid type (list) for variable 'Distance3'

>
Model<-lme(Webslog1~Treatment*Distance,random=~Week|Uniquesite/Uniqueplot,method="REML")

Error in model.frame.default(formula = ~Week + Webslog1 + Treatment +  :
  invalid type (list) for variable 'Distance3'*
*>*


Someone any idea? Bug or just my poor R skills?

Thanks for having a look at this!

Pieter

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