R help - Jun 2007 - Linear Mixed Models with nlme, more than one random effect

Hi, I' trying to learn how to use lme for Linear Mixed Models  and I have a 
problem when I have to include more than one random effect in my model. I 
know that this could be a stupid question to ask, but I'm not able to solve 
it by myself... One example: if my model is

response = operator + block + day
with operator and block as fixed effects and day as random effect, I use

res.lme <- lme(resp ~ oper + block , random=~1|day)

If I want to include also another random effect, as "experiment", what
I
should do ?
This effect doesn't have to be nested, at the and I would like to have the 
COV matrix using (if I'm not wrong) getVarCov function.

Thanks in advance for any help or suggestions, I'm a beginner on this 
field...

Davide

_________________________________________________________________
Cinema, Tv, Gossip e Orsoscopo
Tutto su MSN intrattenimento!

Guilio,

Have a look at Rnew volume 5/1 (http://cran.r-project.org/doc/Rnews/) where
Doug Bates explains this nicely. Condider using lme4 for your purpose.

Joris








                                                                           
             "Giulio Di                                                    
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                                       [R] Linear Mixed Models with nlme,  
                                       more than one random effect         
             20/06/2007 14:09                                              
                                                                           
                                                                           
                                                                           
                                                                           
                                                                           





Hi, I' trying to learn how to use lme for Linear Mixed Models  and I have a

problem when I have to include more than one random effect in my model. I
know that this could be a stupid question to ask, but I'm not able to solve

it by myself... One example: if my model is

response = operator + block + day
with operator and block as fixed effects and day as random effect, I use

res.lme <- lme(resp ~ oper + block , random=~1|day)

If I want to include also another random effect, as "experiment", what
I
should do ?
This effect doesn't have to be nested, at the and I would like to have the
COV matrix using (if I'm not wrong) getVarCov function.

Thanks in advance for any help or suggestions, I'm a beginner on this
field...

Davide

_________________________________________________________________
Cinema, Tv, Gossip e Orsoscopo?Tutto su MSN intrattenimento!

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PLEASE do read the posting guide
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and provide commented, minimal, self-contained, reproducible code.

<joris.dewolf <at> cropdesign.com> writes:
> Have a look at Rnew volume 5/1 (http://cran.r-project.org/doc/Rnews/) where
> Doug Bates explains this nicely. Consider using lme4 for your purpose.
But be aware of
<http://finzi.psych.upenn.edu/R/Rhelp02a/archive/76742.html>
if you currently want to use lme4.

Dieter