Message-ID: <4EC65E72.4010000@agr.uni-goettingen.de>
Date: 2011-11-18T13:32:34Z
From: Christoph Scherber
Subject: repeated measurement using mixed model
In-Reply-To: <4EC5FB57.8070000@yeah.net>
Dear Jinsong Zhao,
In this case, you may wish to use a generalized least squares model (gls), also to be found in the nlme library. You can start with an initial model
containing only fixed effects, and then update it with an appropriate correlation structure.
Try this first:
library(nlme)
?gls
?corStruct
All the best
Christoph
on 18.11.2011 07:29, Jinsong Zhao wrote:
> Hi there,
>
> We have got a valuable data set from a long-term experiment. The
> experimental design is following:
>
> Trt Time Y
> 1 1983
> 1 1986
> 1 1993
> 1 1998
> 1 2003
> 1 2010
> 2 1983
> 2 1986
> 2 1993
> 2 1998
> 2 2003
> 2 2010
> 3 1983
> 3 1986
> 3 1993
> 3 1998
> 3 2003
> 3 2010
>
> Because the data was collected in a way of repeated measurement. we
> think it should be analyzed using linear mixed model. However, there is
> no group variable, and as you have noted, there is no replication for
> each treatment (Trt). So, we don't know how to deal with this data set.
>
> Any suggestions or comments will be really appreciated. Thanks in advance.
>
> Regards,
> Jinsong
>
> _______________________________________________
> R-sig-mixed-models at r-project.org mailing list
> https://stat.ethz.ch/mailman/listinfo/r-sig-mixed-models
>
> .
>
--
Dr. Christoph Scherber
Georg-August-University Goettingen
Department of Crop Science
Agroecology
Grisebachstrasse 6
37077 Goettingen
tel +49 (0)551 39 8807
fax +49 (0)551 39 8806
www.gwdg.de/~cscherb1