[R-sig-ME] Mixed model and Singularity Error message

[ONKELINX, Thierry]

Dear Antoine,

If subsite is nested in site then the interaction between both is pointless. You cannot estimate such interaction. Hence the singularity.

Best regards,

Thierry

ir. Thierry Onkelinx
Instituut voor natuur- en bosonderzoek / Research Institute for Nature and Forest
team Biometrie & Kwaliteitszorg / team Biometrics & Quality Assurance
Kliniekstraat 25
1070 Anderlecht
Belgium
Thierry.Onkelinx at inbo.be
www.inbo.be

To call in the statistician after the experiment is done may be no more than asking him to perform a post-mortem examination: he may be able to say what the experiment died of.
~ Sir Ronald Aylmer Fisher

The plural of anecdote is not data.
~ Roger Brinner

The combination of some data and an aching desire for an answer does not ensure that a reasonable answer can be extracted from a given body of data.
~ John Tukey


-----Oorspronkelijk bericht-----
Van: r-sig-mixed-models-bounces at r-project.org [mailto:r-sig-mixed-models-bounces at r-project.org] Namens Antoine PACCARD
Verzonden: donderdag 8 december 2011 16:38
Aan: r-sig-mixed-models at r-project.org
Onderwerp: [R-sig-ME] Mixed model and Singularity Error message

Dear Mix modelers,

I know that this topic has been discussed in the past but since I cannot find any clear answer yet I am sending this message. I am runing a simple mix model as:

m1 <- lme(fixed=trich~habitat*site*subsite*treatment, random=~1|fam/
id,data=data,na.action=na.exclude)

and I constantly find this error message:"singularity in backsolve at level 0 block 1". I am not sure how to solve the problem. I noticed that it arises only when the variable "subsite" is added.
For clarification, all of my fixed effects are factors (excluding
"trich")

Could anyone help me with that?

Many thanks,
Antoine

_______________________________________________
R-sig-mixed-models at r-project.org mailing list https://stat.ethz.ch/mailman/listinfo/r-sig-mixed-models