[R-sig-ME] Coefficient matrix not invertible

[Rian Dickson]

hello again,

Thanks for the recent answers to my other questions - they've been quite useful.
I've run into another problem a little further along. 

When I try to run this model:

global.ri.vf1.cs1.lme <- lme(Log.minH ~ site + f.year + cohort + emerg + emergSQ + pri + priSQ
  + start.t + startSQ + sea + tidem + tided, data = SUSCforage, random = ~1|scoterID, 
  weights = varExp(form =~Log.minH), correlation = corAR1(form =~ Date|scoterID), method = "REML")

I get this error message:
Error in `coef<-.corARMA`(`*tmp*`, value = 20.3619280472088) : 
  Coefficient matrix not invertible

However, if I try the same model except without the variance weighting, it works fine. 

Also, with the variance weighting included, 
corARMA(form =~ Date|scoterID, p=0, q=1) works
but
corARMA(form =~ Date|scoterID, p=1, q=1) returns a similar error message as above.
Error in `coef<-.corARMA`(`*tmp*`, value = c(21.0236910353017, -6.13825550757903 : 
  Coefficient matrix not invertible


I'm not sure what this means, or if there is anything I can do about it. 
Any advice would be appreciated.

thank you,

Rian

*************************************

Rian Dickson
M.Sc. candidate
Centre for Wildlife Ecology
Department of Biological Sciences
Simon Fraser University
8888 University Drive
Burnaby BC V5A 1S6
778.782.5618