I am trying to run the following model in R
> lmer(leaves.eaten~Geocytotype+(1|TEST/
PLANT),data=cyphoplantfeeding,family=poisson)
My experimental setup is 41 replicates (TEST) of an experiment in
which there are three Geocytotypes of a plant species in each TEST,
and two plant pseudoreplicates per Geocytotype in each test (i.e.
3*2=6 plants per test). So my random factors are trying to examine/
account for variation between replicates and between pairs of plants
in each test. The response variable is counts of damaged leaves on
each plant hence the poisson distribution.
When I try and run the model I get this error message (sorry but it
is in French):
>Erreur : length(f1) == length(f2) is not TRUE
>De plus : Warning messages:
>1: In PLANT:TEST :
> l'expression numérique a 246 éléments : seul le premier est utilisé
>2: In PLANT:TEST :
> l'expression numérique a 246 éléments : seul le premier est utilisé
This however is not connected as far as I can tell to the structure
of the data because I checked the lengths of all the variables and
if I run the same model design using lme function (without the
family=poisson of course) and the model computes perfectly fine with
the correct group sizes:
>Number of Observations: 246
>Number of Groups:
> TEST PLANT %in% TEST
> 41 123
I couldn't find this error mentioned in any other posts on the list.
Can someone enlighten me as to how to get around this intractable
problem? My crude solution is to go around the obstacle by computing
the mean of each plant pair and using a GLM with poisson distribution
and ignore random effects.
Martin
************************************************************************
Martin Henery
Post doctoral researcher
Département de Biologie/Ecologie & Evolution
Université de Fribourg
************************************************************************
[[alternative HTML version deleted]]
______________________________________________
R-help@r-project.org mailing list
https://stat.ethz.ch/mailman/listinfo/r-help
PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
and provide commented, minimal, self-contained, reproducible code.
