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




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