Hi everyone!
I am analyzing nesting success (almost successfully) as you can see in my last post:
viewtopic.php?f=21&t=3284
My set of models from the old post worked perfect, including the full model:
rLD+yr+yr2+rLD:yr+rLD:yr2+NestAge
where
rLD = relative laying date
yr = year
NestAge= nest age
yr2= year squared term (yr^2) to look for non-linearity
and the interactions between rLD:yr and rLD:yr2
However I was asked to include also models where I use relative laying date with a squared term (rLD^2) instead of rLD, also to look for non-linear effect in the season. This is not working anymore. I found that the models that have a problem are those including both interactions when using the rLD^2:
rLD2+yr+yr2+rLD2:yr+rLD2:yr2+NestAge
and
rLD2+yr+yr2+rLD2:yr+rLD2:yr2
the reason to have this model including rLD^2 is because the nesting success - laying date (rLD) relationship for every year is non-linear and we want to look for systematic changes over time in this relationship.
Can you please give me some advice?