Hi everyone,
I'm using lmer and estimable (from packages lme4 and gmodels respectively) and
have the disconcerting happening that when I run exactly the same code, I get
different results! In checking this out by running the code 50x, it seems to
be that answers may be randomly deviating around those which I get from another
stats package (GenStat, using the linear mixed models functionality in this).
As such, my guess is that perhaps there is a random seed involved somewhere in
the estimable function, and that the answer is simply converging to a slightly
different place each time, based on a slightly different starting place. But
this is only a guess - if anyone could either confirm or otherwise explain this
unexpected-to-me happening, that'd be fantastic!!
The code that I'm running is:
design.1 = rbind(c(0,0,0,1,0,0,0,0,0,0,0,0))
lme1 <- lmer(var_x~AGE*GENDER*DAM_DIET + (1|CHIP) + (1|LITTER),x_temp)
est <- estimable(lme1,design.1)
print(est)
est <- estimable(lme1,design.1) # Repeat of code
print(est)
est <- estimable(lme1,design.1) # Another repeat of code
print(est)
And this is the output - you can see in this that the results vary each time
the code is run...
> print(est)
Estimate Std. Error p value
(0 0 0 1 0 0 0 0 0 0 0 0) 0.02241752 0.2185279 0.902
> est <- estimable(lme1,design.1)
> print(est)
Estimate Std. Error p value
(0 0 0 1 0 0 0 0 0 0 0 0) 0.001824573 0.2106973 0.974
> est <- estimable(lme1,design.1)
> print(est)
Estimate Std. Error p value
(0 0 0 1 0 0 0 0 0 0 0 0) 0.01276941 0.2154196 0.938
My SessionInfo is as follows:
R version 2.9.2 (2009-08-24)
i386-pc-mingw32
locale:
LC_COLLATE=English_New Zealand.1252;LC_CTYPE=English_New
Zealand.1252;LC_MONETARY=English_New
Zealand.1252;LC_NUMERIC=C;LC_TIME=English_New Zealand.1252
attached base packages:
[1] splines stats graphics grDevices utils datasets tcltk
methods base
other attached packages:
[1] lme4_0.999375-32 Matrix_0.999375-31 lattice_0.17-25 multcomp_1.1-2
survival_2.35-7 mvtnorm_0.9-7 gmodels_2.15.0 svIDE_0.9-5
loaded via a namespace (and not attached):
[1] gdata_2.4.2 grid_2.9.2 gtools_2.6.1 MASS_7.2-48 svMisc_0.9-5
Many thanks for any help or advice that anyone can provide :)
Cheers,
Zaneta
____________________________
Zaneta Park
Biometrician
T +64 6 351 8008
E zaneta.park...@agresearch.co.nz
AgResearch Limited
Grasslands Research Centre
Tennent Drive, Private Bag 11008, Palmerston North, New Zealand
T +64 6 356 8019 F +64 6 351 8032 www.agresearch.co.nz
Farming Food and Health. First
Te Ahuwhenua Te Kai me te Whai Ora. Tuatahi
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