[R-sig-ME] Interaction between random and fixed effects
th|erry@onke||nx @end|ng |rom |nbo@be
Mon May 31 21:10:13 CEST 2021
What did you ran the interaction as a fixed effect Year:Local or a
random effect (1|Year:Local)? How did you code Local: as a unique value
for every Local and Year combinations? Please do share output or a minimal
example so we know exactly what you did. I'm still a novice at mind reading.
ir. Thierry Onkelinx
Statisticus / Statistician
Vlaamse Overheid / Government of Flanders
INSTITUUT VOOR NATUUR- EN BOSONDERZOEK / RESEARCH INSTITUTE FOR NATURE AND
Team Biometrie & Kwaliteitszorg / Team Biometrics & Quality Assurance
thierry.onkelinx using inbo.be
Havenlaan 88 bus 73, 1000 Brussel
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
Op ma 31 mei 2021 om 20:57 schreef Vinicius Maia <
vinicius.a.maia77 using gmail.com>:
> Hi all,
> I have a subtle doubt in how to interpret the interaction between fixed (or
> even random) and random effects in the following case.
> I have a model: Y ~ Year + (1|Local)+(1|Genotype) + (Year:Local:Genotype)
> Year is a fixed effect because it has only 4 levels.
> I ran the model with the random and fixed effect interaction just to
> explore, but I was not expecting that it would work because Locals are
> completely nested within Years.
> To my surprise, the model ran and the variance of Year:Local:Genotype are
> quite big. How is it possible to have Local interacting with Year if they
> are nested? I also tried: Y ~ Year + (1|Local)+(1|Genotype) + (Year:Local)
> and the model rans too, without singular fit.
> I am struggling to understand if random interactions (it also extends to
> cases where the interactions are only between nested random effects) mean
> that the variance between Locals changes with Years or if the effect of a
> given Local changes with Years. If it is the former option I can understand
> why the model ran and has a high variance for the interaction, but if it is
> the later case (which I believe it is), how does the model estimate an
> interaction for Local:Year if they are nested?
> Best wishes,
> Vinícius Maia
> [[alternative HTML version deleted]]
> R-sig-mixed-models using r-project.org mailing list
[[alternative HTML version deleted]]
More information about the R-sig-mixed-models