repeated measurement using mixed model
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
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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