[R-sig-ME] Offset() in gls() in nlme

[Mark Payne]

Hi Douglas,

Thanks for the reply - unfortunately there doesn't seem to be an offset 
argument either in the latest version of nlme... :-(

 > gls
function (model, data = sys.frame(sys.parent()), correlation = NULL,
     weights = NULL, subset, method = c("REML", "ML"), na.action = na.fail,
     control = list(), verbose = FALSE)

 > packageDescription("nlme")
Package: nlme
Version: 3.1-118
Date: 2014-10-07

Mark


On 13/11/14 04:54, Douglas Bates wrote:
> It may work if  you use the offset argument instead of putting an offset
> term in the formula.  The model-fitting code in R (and S before it)
> sometimes has the "there's more than one way to do it" approach of
> Perl.  This is convenient for users but not for those writing the code.
> I believe we implemented the offset argument form.
>
> On Wed Nov 12 2014 at 2:52:30 AM ONKELINX, Thierry
> <Thierry.ONKELINX at inbo.be <mailto:Thierry.ONKELINX at inbo.be>> wrote:
>
>     Dear Mark,
>
>     In case of a linear model you can create a new variable Y = R - ssb
>     and model Y without offset instead of R with ssb as offset. That
>     should give the same parameter estimates.
>
>     Best regards,
>
>     ir. Thierry Onkelinx
>     Instituut voor natuur- en bosonderzoek / Research Institute for
>     Nature and Forest
>     team Biometrie & Kwaliteitszorg / team Biometrics & Quality Assurance
>     Kliniekstraat 25
>     1070 Anderlecht
>     Belgium
>     + 32 2 525 02 51
>     + 32 54 43 61 85
>     Thierry.Onkelinx at inbo.be <mailto:Thierry.Onkelinx at inbo.be>
>     www.inbo.be <http://www.inbo.be>
>
>     To call in the statistician after the experiment is done may be no
>     more than asking him to perform a post-mortem examination: he may be
>     able to say what the experiment died of.
>     ~ Sir Ronald Aylmer Fisher
>
>     The plural of anecdote is not data.
>     ~ Roger Brinner
>
>     The combination of some data and an aching desire for an answer does
>     not ensure that a reasonable answer can be extracted from a given
>     body of data.
>     ~ John Tukey
>
>     -----Oorspronkelijk bericht-----
>     Van: r-sig-mixed-models-bounces at r-__project.org
>     <mailto:r-sig-mixed-models-bounces at r-project.org>
>     [mailto:r-sig-mixed-models-__bounces at r-project.org
>     <mailto:r-sig-mixed-models-bounces at r-project.org>] Namens Mark Payne
>     Verzonden: dinsdag 11 november 2014 13:23
>     Aan: r-sig-mixed-models at r-project.__org
>     <mailto:r-sig-mixed-models at r-project.org>
>     Onderwerp: [R-sig-ME] Offset() in gls() in nlme
>
>     Hi,
>
>     I am trying to use the following model formula in gls() in the nlme
>     package:
>
>     R ~ Turb + offset(ssb)
>
>     Unfortunately, gls() seems to ignore the offset argument and give
>     results that are identical to
>
>     R ~ Turb
>
>     This is not the case when I use lm() - however, I would like to
>     include a
>     corAR1() term as well, which is why I am using gls().
>
>     Is this known and intended behaviour? If so, is there a recommended
>     workaround/alternative?
>
>     Best wishes,
>
>     Mark
>
>              [[alternative HTML version deleted]]
>
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