Diederik, The `gamm' call looks fine provided `park' is nested in `count'. You are basically adding a random effect for each survey, and a random effect for each `park' within survey to the the smooth effects.
best, Simon ps. I assume there are more than 18 observations in the full dataset --- the model sturcture is a bit too complicated otherwise... On Wednesday 28 January 2009 19:44, Strubbe Diederik wrote: > Dear Simon, > Many thanks for pointing me to the GAMM! For clarification, Bird_abundance > are breeding densities ( e.g. 1.25 BP/ha, 2.20 BP/ha,...) and count is just > the actual survey(e.g. first_survey,...). The dataset looks like > Bird_abundance Study_area YEAR COUNT X1 X2 X3 > X4 > 0.15 area_1 2004 first_survey � � � � > 1.26 area_1 2004 second_survey � � � � > 2.47 area_1 2005 third_survey � � � � > 0.00 area_1 2005 fourth_survey � � � � > 0.23 area_1 2006 fifht_survey � � � � > 2.64 area_1 2006 sixth_survey � � � � > 4.14 area_2 2004 first_survey � � � � > 5.00 area_2 2004 second_survey � � � � > 6.80 area_2 2005 third_survey � � � � > 0.15 area_2 2005 fourth_survey � � � � > 0.25 area_2 2006 fifht_survey � � � � > 2.36 area_2 2006 sixth_survey � � � � > 2.59 area_3 2004 first_survey � � � � > 6.31 area_3 2004 second_survey � � � � > 0.15 area_3 2005 third_survey � � � � > 2.85 area_3 2005 fourth_survey � � � � > 2.48 area_3 2006 fifht_survey � � � � > 1.23 area_3 2006 sixth_survey � � � � > � � � � � � � � > > Am I correct in assuming the following is a valid syntax for this repeated > measures design?: > > model <-gamm(Bird_abundance ~ YEAR + s(X1)+ s(X2)+ s(X3)+ > s(X4),random=list(count=~1,park=~1)) > > best wishes and thanks again, > > Diederik > > > > > > Diederik Strubbe > Evolutionary Ecology Group > Department of Biology, University of Antwerp > Universiteitsplein 1 > B-2610 Antwerp, Belgium > http://webhost.ua.ac.be/deco > tel : 32 3 820 23 85 > > > > -----Original Message----- > From: Strubbe Diederik > Sent: Wed 28-1-2009 18:09 > To: r-help@R-project.org > Subject: Repeated measures design for GAM? - corrected question... > > Dear all, > > I have a question on the use of GAM with repeated measures. My dataset is > as follows: - a number of study areas where bird abundance has been > determined. Counts have been performed in 3 consecutive years and there > were 2 counts per year (i.e. in total 6 counts). - a number of > environmental predictors that do not change over year Xi). When using a > GLM, a repeated measures design would like: (for example) > > lme(Bird_abundance = study_area + count +year+ X1 + X2 + X3,random = > ~count|study_area). > > However, I have found no analogue design for a GAM. For now, I have > averaged my bird abundances but I wondered whether a more subtle and > elegant strategy exists...? > > Many thanks, > > > Diederik > > Diederik Strubbe > Evolutionary Ecology Group > Department of Biology, University of Antwerp > Universiteitsplein 1 > B-2610 Antwerp, Belgium > http://webhost.ua.ac.be/deco > tel : 32 3 820 23 85 > > > > > [[alternative HTML version deleted]] -- > Simon Wood, Mathematical Sciences, University of Bath, Bath, BA2 7AY UK > +44 1225 386603 www.maths.bath.ac.uk/~sw283
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