Does lmer have it's own random number generator?

<Thierry.ONKELINX at ...> wrote:

Are you sure? Below the results of 100 simulations. 
I get the same results each time.

set.seed(1)
tmp <- replicate(100, {

+ ? ? ? fit <- lmer(
+ ? ? ? ? ? ? ? formula = rt ~ (1|subnum) +
+ ? ? ? ? ? ? ? ? ? ? ? cue*flank*group*block +
+ ? ? ? ? ? ? ? ? ? ? ? cue*flank*group*I(block^2) +
+ ? ? ? ? ? ? ? ? ? ? ? cue*flank*group*I(block^3)
+ ? ? ? ? ? ? ? , data = ANT[ANT$error==0,]
+ ? ? ? )
+ ? ? ? fit <at> deviance })

apply(tmp, 1, var)

? ? ? ML ? ? ?REML ? ? ?ldL2 ? ? ldRX2 ? sigmaML sigmaREML ? ? pwrss
disc
? ? ? ?0 ? ? ? ? 0 ? ? ? ? 0 ? ? ? ? 0 ? ? ? ? 0 ? ? ? ? 0 ? ? ? ? 0
0
? ? usqr ? ? ?wrss ? ? ? dev ? ? ?llik ? NULLdev
? ? ? ?0 ? ? ? ? 0 ? ? ? ?NA ? ? ? ?NA ? ? ? ?NA

sessionInfo()

R version 2.12.0 (2010-10-15)
Platform: i386-pc-mingw32/i386 (32-bit)
locale:
[1] LC_COLLATE=Dutch_Belgium.1252 ?LC_CTYPE=Dutch_Belgium.1252
[3] LC_MONETARY=Dutch_Belgium.1252 LC_NUMERIC=C
[5] LC_TIME=Dutch_Belgium.1252

[mailto:r-sig-mixed-models-bounces at ...] Namens Mike Lawrence
Verzonden: maandag 3 januari 2011 3:52
Aan: r-sig-mixed-models at ...
Onderwerp: [R-sig-ME] Does lmer have it's own random number generator?
Does lmer have it's own internally seeded random number
generator? I just came across an example where I get
different results across repeated identically specified lmer
fits even when I use set.seed():

any(is.finite(attr(fit,'deviance')))

A call to lmer does not, as far as I know, result in any calls to
random number generators.  There is only one point in the lme4 package
where set.seed is called and that is in the simulate method.