[R] nlme model specification

From: Martin Henry H. Stevens <hstevens_at_muohio.edu>
Date: Thu 18 May 2006 - 06:51:55 EST


Hi folks,
I am tearing my hair out on this one.
I am using an example from Pinheiro and Bates.

### this works
data(Orange)
mod.lis <- nlsList(circumference ~ SSlogis(age, Asymp, xmid, scal),

             data=Orange )

### This works
mod <- nlme(circumference ~ SSlogis(age, Asymp, xmid, scal),

             data=Orange,
             fixed = Asymp + xmid + scal ~ 1,
             start = fixef(mod.lis) )

### I try a slightly different model specification for the fixed effects, and it does not work.
### fixed = list(Asymp ~ 1, xmid ~ 1, scal ~ 1) ### I tried following the example on page 355.

mod <- nlme(circumference ~ SSlogis(age, Asymp, xmid, scal),

             data=Orange,
             fixed = list(Asymp ~ 1, xmid ~ 1, scal ~ 1),
             start = fixef(mod.lis) )

### I get
Error in parse(file, n, text, prompt) : syntax error in "~ "

nlme version 3.1-71

> version

                _
platform       powerpc-apple-darwin8.6.0
arch           powerpc
os             darwin8.6.0
system         powerpc, darwin8.6.0
status
major          2
minor          3.0
year           2006
month          04
day            24
svn rev        37909
language       R

version.string Version 2.3.0 (2006-04-24)
>

Dr. M. Hank H. Stevens, Assistant Professor 338 Pearson Hall
Botany Department
Miami University
Oxford, OH 45056

Office: (513) 529-4206
Lab: (513) 529-4262
FAX: (513) 529-4243

http://www.cas.muohio.edu/~stevenmh/
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http://www.muohio.edu/botany/

"E Pluribus Unum"

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