R help - Nov 2008 - repeated measures regression and power analysis?

Hi there,
 
I am attempting to assess whether there is a trend in a
observations of a population that was observed on 7 consecutive days in July
for 6 years (2000, 2001, 2002, 2004, 2006, 2008).  I have count data of
the number of observations per day for each of the seven days for each of the 6
years (total of 42 days of count data).   Is there a package in R
that can accomplish this?  I have been looking through repeated measures
regression threads, but nothing seems quite right.  
 
Also, is there a package/method that would allow me to
conduct a power analysis regarding how many more years of data would be
required to detect a trend of a certain magnitude? 
 
Thanks!
 
Jake


      
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Dear Jake,

Have a look at glmer in the lme4 package. The will allow you to model
the trend with repeated measurements.

The easiest way to do some power analysis for repeated measurement will
probably be by simulation.

HTH,

Thierry


------------------------------------------------------------------------
----
ir. Thierry Onkelinx
Instituut voor natuur- en bosonderzoek / Research Institute for Nature
and Forest
Cel biometrie, methodologie en kwaliteitszorg / Section biometrics,
methodology and quality assurance
Gaverstraat 4
9500 Geraardsbergen
Belgium 
tel. + 32 54/436 185
Thierry.Onkelinx op 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-help-bounces op r-project.org [mailto:r-help-bounces op r-project.org]
Namens Jake Verschuyl
Verzonden: maandag 24 november 2008 20:46
Aan: r-help op r-project.org
Onderwerp: [R] repeated measures regression and power analysis?

Hi there,

I am attempting to assess whether there is a trend in a
observations of a population that was observed on 7 consecutive days in
July
for 6 years (2000, 2001, 2002, 2004, 2006, 2008).  I have count data of
the number of observations per day for each of the seven days for each
of the 6
years (total of 42 days of count data).   Is there a package in R
that can accomplish this?  I have been looking through repeated measures
regression threads, but nothing seems quite right.  

Also, is there a package/method that would allow me to
conduct a power analysis regarding how many more years of data would be
required to detect a trend of a certain magnitude? 

Thanks!

Jake


      
	[[alternative HTML version deleted]]

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