Dear friends,
In gls() of nlme package, there is some explanation on correlation:
gls(model, data, correlation, weights, subset, method, na.action, control,
verbose)
correlation: an optional 'corStruct' object describing the within-group
correlation structure. See the documentation of 'corClasses'
for a description of the available 'corStruct' classes. If a
grouping variable is to be used, it must be specified in the
'form' argument to the 'corStruct' constructor.
Defaults to
'NULL', corresponding to uncorrelated errors.
Now i have two categorical variables: grass and altitude,
*gls.fit
<-gls(log(snail)~grass+altitude+gheight+humidity+soiltemr+airtemr,data=model,correlation=corAR1(
form=~grass+altitude))*
Is the above argument that i use right?
thanks very much!
--
Kind Regards,
Zhi Jie,Zhang ,PHD
Department of Epidemiology
School of Public Health
Fudan University
Tel:86-21-54237149
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