[R] addressing and summarizing columns of a dataframe in nlme package

[Eva Remke]

Hi!

Within the lm function I can address and summarize columns like that:

 >lm1<-lm(I(rowSums(spec[,5:81]))~pH)


If I want to do the same in nlme package I get the following error:

 > lme1<-lme(I(rowSums(spec[,5:81]))~pH,random=~1|site)
Error in model.frame.default(formula = ~spec + pH + site, data = 
<environment>,  :
   invalid type (list) for variable 'spec'

These kind of list seem to be not accepted by the lme function and my 
formula misinterpreted.
Variables are "pH" and "site", dataframe is "spec" and attached.

How can I address and summarize any number of columns of a dataframe in 
the nlme package?


Thanks a lot, cheers
Eva


-- 
Eva Remke

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