From: emma pilgrim (IGER-NW) <emma.pilgrim_at_bbsrc.ac.uk>

Date: Fri 18 Mar 2005 - 01:03:17 EST

R-help@stat.math.ethz.ch mailing list

https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide! http://www.R-project.org/posting-guide.html Received on Fri Mar 18 01:10:20 2005

Date: Fri 18 Mar 2005 - 01:03:17 EST

Hello

I am looking at soil mineral data were collected : 99, 02, 04.

For the magnesium soil data, I have created the following groupedData object:

magnesium<-groupedData(Mg~year|treatment, inner=~block) Where mg=magnesium Kg/ha

As it is a repeated measures I was going to use an lme. I have looked at Pinherio and Bates : Mixed-Effects models in S and S-plus and I am getting slightly confused. In order to fit the lme, should I specify the data to use in the model as the grouped structure model?

If so is the following command correct:

Model1<-lme(mg~treatment, random=block|year, data=magnesium)?

I am slightly worried that it isn't, because in model summary, instead of listing the 19 different treatments in the fixed effects section, it writes intercept (as normal), then treatment^1, treatment^2 etc.

However if I don't specify the groupedData object in the model, then in the fixed effects section, it names the treatments (i.e. intercept, treatmentcontrol, treatment6TFYM.

Should I be fitting the model using the whole data set rather than the groupedData object?

Thank you very much for your help

Emma Pilgrim

Dr Emma Pilgrim

Plant Ecologist

**IGER
**

North Wyke

Okehampton

EX20 2SB

email: emma.pilgrim@bbsrc.ac.uk

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R-help@stat.math.ethz.ch mailing list

https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide! http://www.R-project.org/posting-guide.html Received on Fri Mar 18 01:10:20 2005

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