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

From: Douglas Bates <bates_at_stat.wisc.edu>
Date: Tue 03 Apr 2007 - 16:57:50 GMT

On 4/3/07, Fang, Yongxiang <y.fang@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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