[R] Multiple comparison for circular data

[Spencer Graves]

	  I just got 141 hits from 'RSiteSearch("circular data")'.  From this, 
I quickly learned of two contributed packages for circular data: 
"circular" and "CircStats".  Both seem to be current, and both are 
maintained by the same person.

	  If you can compute a likelihood for a particular model, then you can 
test for equality of parameters between two data sets as follows:

	  logLik1 = log(likelihood for data set 1 fit by itself.
	  logLik2 = log(likelihood for data set 2 fit by itself.
	  logLik12= log(likelihood for data sets 1 and 2 fit as one.

	  log(likelihood ratio) = (logLik1+logLik2-logLik12).

	  If k parameters are fit for each model, then 2*log(likelihood ratio) 
should be approximately chi-square(k).  From this you can get a p-value 
to compare any pair of data sets.  Then use Bonferroni, multiplying each 
p-value by, say, (k-1).  Any p-value(s) below your Bonferroni-adjusted 
threshold could be claimed to be significantly different.

	  If this is not adequate, I suggest you download both packages (if you 
have not already), try them, and then send a question to the maintainer. 
  If you would like more help from the listserve, I suggest you PLEASE 
do read the posting guide! "www.R-project.org/posting-guide.html". 
Also, please install the "fortunes" package and read especially 
fortune('posting').

	  hope this helps.
	  spencer graves

ecoinfo wrote:

> Hi All,
> 
> Does anyone know how to compare the means of several circular-data
> samplings? Any related websites, references and softwares?
> 
> Thanks
> Xiaohua
> 
> --
> Xiaohua Dai, Dr.
> 
> 	[[alternative HTML version deleted]]
> 
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