[R-sig-ME] lmer/lmer2 timing results

[Reinhold Kliegl]

Not sure whether this is still of interest. There was some interest  
about speed of lmer and lmer2. Attached are comparisons for seven  
rather complex models estimated from a set of eye fixations measured  
during reading isolated sentences  (N=29114 reading fixations; 3  
random partially crossed groups of 109 subjects, 144 sentences, and  
550 words. Note that most words occur only in one sentence but some  
words (e.g., articles) can also occur more than once per sentence.  
Also, for all subjects some of the sentences are missing. In addition  
to the three intercept variances, I always estimated subject  
variances  for three slopes with their covariances forced to zero.  
The models all use the same predictors; they differ in what subset of  
fixed effects of the full factorial is estimated. The number of model  
parameters (fixed and random effects) varies from 406 to 158.  I am  
quite amazed that there were absolutely no problems with convergence,  
etc.. (It is also nice that the results make a lot of sense, too.)

lmer2 was faster than lmer on the largest model (588 vs. 642). For  
the smaller models lmer was typically faster than lmer2  but not  
always. Given its overall speed even for such complex models, the  
timing differences are not important for these data. Most  
importantly, the estimates are incredibly similiar for all seven  
models. Details (fit statistcs and random effects for lmer and lmer2,  
but not fixed-effect estimates) are given in the attachment.

R version 2.4.1 Patched (2007-01-26 r40579)
i386-apple-darwin8.8.1, lme4 0.9975-13.

Best
Reinhold
----
Reinhold Kliegl, Dept. of Psychology, University of Potsdam,
Karl-Liebknecht-Strasse 24-25, 14476 Potsdam, Germany
phone: +493319772868, fax: +493319772793
http://www.psych.uni-potsdam.de/people/kliegl/



----
Reinhold Kliegl, Dept. of Psychology, University of Potsdam,
Karl-Liebknecht-Strasse 24-25, 14476 Potsdam, Germany
phone: +493319772868, fax: +493319772793
http://www.psych.uni-potsdam.de/people/kliegl/