Ana
You are estimating a random coefficient model on 5 individuals (mean
and variance). Are you sure this is wise?
Ross Darnell
----- Original Message -----
From: Ana Conesa <aconesa at ochoa.fib.es>
Date: Thursday, July 5, 2007 1:21 am
Subject: [R] questions on lme function>
> Dear list,
>
> I am using the lme funcion to fit a mixed model for the time response
> of a number of physiological variables. The random variable would be
> the individual on which physiological variables are measured at
> different time points. I have 4 time points, 5 individuals and 3
> replicates per condition (time/individual), and I would like to fit
> a quadratic model on time. The model I am using is
>
> > mm <- lme(myvar ~ time + time2, random= ~ time|individual,
> data=clinical)
>
> being time2 = time*time
>
> I have a number of questions
>
> 1) I am not very sure the random effect is correctly modeled.
> Would I
> need to include the time2 variable aswell?
>
> 2) I would like to extract the F statistics of the model, and I do
> not find a function for this. Is this possible?
>
> 3) depending of the variable I take, I frequently obtain a
> convergence error as a result of the lme funcion. Any ideas on what
> to do to improve convergence?
>
> Thank you
>
> Ana Conesa, PhD
> Centro de Investigacion Principe Felipe
> Avda. Autopista Saler 16 46013 Valencia
> http://bioinfo.cipf.es
>
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