Offset() in gls() in nlme

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
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] Namens Mark Payne
Verzonden: dinsdag 11 november 2014 13:23
Aan: 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]]