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mixed model

1 message · Doran, Harold

Doran, Harold
# 
I may not follow entirely here, but your random effects structure isn't
correct for lme. Also, nlme cannot handle (at least well) models with
crossed random effects. A better option would be to use the lmer
function. 

Setting up the structure for the random effects in nlme would look
something like:

lme(y~ fixed, data, random~= z1 + z2 |ID)

Where ID is a variable that contains the grouping structure of your
data.

In lmer, which is more appropriate for models with crossed random
effects, you lmer call might be something along the lines of:

lmer(y ~ fixed + (z1|ID) + (z2|ID), data)

See the most recent version of R news for more info on this topic.

-----Original Message-----
From: r-help-bounces at stat.math.ethz.ch
[mailto:r-help-bounces at stat.math.ethz.ch] On Behalf Of NATALIA F
TCHETCHERINA
Sent: Wednesday, May 25, 2005 11:50 AM
To: r-help at stat.math.ethz.ch
Subject: [R] mixed model

 Hello all,
 I have problem with setting up random effects.
 I have a model:
 y=x1+x2+x1*x2+z1+z1*x2
 where x1, x2, x1*x2 are fixed effects
 and z1, z1*x2 are random effects (crossed effects)  I use library(nlme)
'lme' function.
 My question is: how I should set up random effects?
 I did
 lme(y~x1+x2+x1:x2, data=DATA, random=~z1+z1:x2, na.action='na.omit')
but it did not work.

 Sincerely, Natalia.

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