[R] the numimum number of fixed factors lme package can deal with

Douglas Bates bates at stat.wisc.edu
Tue Apr 3 18:57:50 CEST 2007

On 4/3/07, Fang, Yongxiang <y.fang at lancaster.ac.uk> wrote:

> In my study, mixed effects model is required and the number of fixed
> effects is very large. When lme package is employed, a model error is
> displayed once the number of fixed  factors in the formula reaches 200. Is
> this the maximum number of fixed factors can be handled by lme package?
> If not, what is possible reason of the error message?

What error message?  You didn't tell use what you did and what
happened.  Please read and follow the instructions in the posting
guide - otherwise we will only be able to guess at what the problem
may be.

There is no specific limit of 200 fixed factors (perhaps you mean 200
columns in the model matrix for the fixed effects?) in lme.  However
there will be limits on the amount of memory available to store the
model matrices and associated structures needed to fit the model.

The first thing I would suggest is determining why you want to fit a
model with 200 (or possibly more if you really meant 200 fixed
factors) fixed effects.  It is rare to want to examine such a large
number of coefficients.  Frequently the number of coefficients gets to
this order because you have a factor with a large number of levels, in
which case why not model such a factor with random effects?

You could also try using the lmer function from the lme4 package
instead of lme to fit a linear mixed model.  It is generally more
efficient than lme in both time and storage.

However, before we can help you much you will need to be much more
specific in your question and provide us with the recommended
background information.

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