Re: [R] lme and confidence intervals

From: Dieter Menne <dieter.menne_at_menne-biomed.de>
Date: Tue, 08 Apr 2008 17:34:19 +0000 (UTC)

Cristian Carranza <cristiancarranza_1 <at> hotmail.com> writes:
> After fitting a mixed effects model to repeated measurements data set, and
after several unsuccessful
> atempts to make a simple plot of the confidence interval for the fitted model,
I gave up and now I am asking
> for help in this useful list.
>
> Could anyone be so kind to give me some code lines in order to make a plot of
the fitted equation and the
> correspondent confidence interval?

The fitted equation is simple: use predict in its variations. For the "confidence interval", most people on the list will ask back what it means. But I know my colleagues, they or their reviewers insist on having error bar in the graphics, and don't care about the interpretation.

Dimitri has given an approach that could be used to produce some reviewer-satisfaction plots limited borborygmy.

http://finzi.psych.upenn.edu/R/Rhelp02a/archive/118174.html

Note that his method is meant to estimate well-defined confidence intervals for the coefficients, but you can use the profiled fits and compute the "confidence intervals" at the data points. Alternatively, you could use mcmc to get a range of curves for averaging.

Dieter



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