Dear Joshua,
Crossed random effects are difficult to specify in nlme. I think that you
have to use pdBlocked() in the specification.
When I need correlation I often use INLA (r-inla.org). It allows for
correlated random effects. Crossed random effects are no problem.
Best regards,
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
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
2017-08-10 23:05 GMT+02:00 Joshua Rosenberg <jmichaelrosenberg at gmail.com>:
Hi all,
I'm trying to fit models with a) crossed random effects and b) a specific
residual structure (auto-correlation). Based on my understanding of what
nlme and lme4 do well, I would normally turn to lme4 to fit a model with
crossed random effects, but because I'm trying to structure the residuals,
I am trying nlme.
In trying to fit and compare the same variance components (no fixed
effects) model using lme4 and nlme, I found the output is similar but a
bit
different. Specifically, the standard deviations of the random effects and
the log-likelihood statistics are different. Would you expect the output
to
be a bit different?
The models I fit to compare the output are here, though the output is also
here:
https://bookdown.org/jmichaelrosenberg/comparing_crossed_effects_models/
library(lme4)
library(nlme)
m_lme4 <- lmer(diameter ~ 1 + (1 | plate) + (1 | sample), data =
Penicillin)
m_lme4
m_nlme <- lme(diameter ~ 1, random = list(plate = ~ 1, sample = ~ 1), data
= Penicillin)
m_nlme
?Thank you for considering this question,
Josh?
--
Joshua Rosenberg, Ph.D. Candidate
Educational Psychology
?&?
Educational Technology
Michigan State University
http://jmichaelrosenberg.com
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