[R-sig-ME] NLME model syntax

[nrm2010]

Yes, I did try that and I had the same problem.
I also tried it without the "list", as in "fixed = list...", based on
previous bug reports, and that doesn't run either.
But if I linearize it and use lme instead of nlme, it runs perfectly.

Also, since I failed to mention this in the original message,
it's nlme v. 3.1-98, R v.  2.11.1 with TINN-R interface on Windows OS.

Thank you.

Toby



---- On Fri, 25 Feb 2011 02:29:37 -0700  Thierry ONKELINX  wrote ---- 

>Have you tried to use a regular data.frame instead of a groupedData object? 
> 
>Best regards, 
> 
>Thierry 
> 
>---------------------------------------------------------------------------- 
>ir. Thierry Onkelinx 
>Instituut voor natuur- en bosonderzoek 
>team Biometrie & Kwaliteitszorg 
>Gaverstraat 4 
>9500 Geraardsbergen 
>Belgium 
> 
>Research Institute for Nature and Forest 
>team Biometrics & Quality Assurance 
>Gaverstraat 4 
>9500 Geraardsbergen 
>Belgium 
> 
>tel. + 32 54/436 185 
>Thierry.Onkelinx at inbo.be 
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> 
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> 
>> -----Oorspronkelijk bericht----- 
>> Van: r-sig-mixed-models-bounces at r-project.org 
>> [mailto:r-sig-mixed-models-bounces at r-project.org] Namens nrm2010 
>> Verzonden: donderdag 24 februari 2011 23:16 
>> Aan: r-sig-mixed-models at r-project.org 
>> Onderwerp: [R-sig-ME] NLME model syntax 
>> 
>> 
>> Hello, 
>> 
>> I'm trying to use NLME for a non-linear model with one random 
>> effect that is the same as the one grouping level (chamber). 
>> Using the following 
>> statement: 
>> 
>> test <- nlme(flux ~ b0 * exp((b1*soiltemp) - (b2*soiltemp^2)) 
>> * vpd^b3 * mstsoil2^b4 * airtemp^b5, data = ac5, fixed = 
>> list(b0 + b1 + b2 + b3 + b4 + b5 ~ 1), random = chamber ~ 1, 
>> start = c(b0 = 570, b1 = 0.08, b2 = 0.002, 
>> b3 = -0.06, b4 = 3, b5 = 0.3), subset = airtemp > 0) 
>> 
>> I always get the error message 
>> "Error in eval(expr, envir, enclos) : object 'chamber' not found" 
>> 
>> Data "ac5" is a groupedData object with chamber as the 
>> grouping factor: 
>> 
>> > head(ac5) 
>> Grouped Data: flux ~ soiltemp + vpd + mstsoil2 + airtemp | chamber 
>> 
>> I've tried many variations such as 
>> random = list(chamber ~ 1) or random = ~1|chamber 
>> or adding the "groups" statement or trying to put chamber on the 
>> RHS of the model statement, after the fixed effects, 
>> but I always get the same error message. 
>> 
>> What is the correct way to formulate the call to nlme? Or is 
>> this not a syntax error? 
>> 
>> Thank you in advance. 
>> 
>> Toby Gass 
>> 
>> tobygass at cnr dot colostate dot edu 
>> 
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>>