[R] Problems with corARMA

Constantinos Antoniou
Mon, 11 Jul 2005 14:06:41 -0000

Dear All,

I just came across the same error message (running a gnls{nlme}
model). [R-2.1.1 on Mac OS 10.4]

For a reproducible example, please download the file:

http://mit.edu/costas/www/GR.txt

and run the following:


GR <- read.table("GR.txt",header=T)
attach(GR)
myyear <- year-1969

library(nlme)
gnls4a <- gnls(fatalities/vehicles1000~a0*(vehicles1000/
population1000)^a1,start=c
(a0=1,a1=1),data=GR,na.action=na.omit,correlation=corARMA(form=~myyear))


Thanks a lot,

Costas



On 10  2005, at 8:43 , Pamela McCaskie wrote:

> Dear all
> I am tryiing to fit the following lme with an ARMA correlation
> structure:
>
> test <- lme(fixed=fev1f~year, random=~1|id2, data=pheno2,
> correlation=corARMA(value=0.2, form=~year|id2), na.action=na.omit)
>
> But I get the following error message:
>
> Error in getGroupsFormula.default(correlation, asList = TRUE) :
>         "Form" argument must be a formula
>
> I have used this same form argument with differerent correlation
> structures and it has worked fine. Does anyone know why it won't
> recognise ~year | id2 (or even ~ 1 | id2) as a formula?
>
> Any help would be great
> Pam
>
> --
> Pamela A McCaskie
> BSc(Mathematical Sciences)(Hons)
>
> Western Australian Institute for Medical Research
> University of Western Australia
> SCGH Campus
> Ground Floor, B Block
> QE-II Medical Centre
> Hospital Avenue, Nedlands
> Western Australia  6009
> AUSTRALIA
> Email:        pmccask at cyllene.uwa.edu.au
> Phone:        +61-8-9346 1612
> Mob:          0417 926 607
>
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--
Constantinos Antoniou, Ph.D.
Massachusetts Institute of Technology
Intelligent Transportation Systems Program
77 Massachusetts Ave., Rm. 1-249, Cambridge, MA 02139