[R-sig-eco] clumping vs. random

[Nicholas Lewin-Koh]

Hi Kristen,
Are you are just interested in "clumpiness" in time, or "clumpiness"
in space and time? Are your sites far enough apart that the
environmental process
you are looking at can be assumed independent? If you have the spatial
coordinates, even approximate, you could calculate Moran's I for the
whole data
set which would give you a rough estimate of the tendency for 1's and
0's 
to cluster together, on average. But that won't tell you a lot about the
behavior
of the process. A little more information about the study would help to
give you a more specific answer.

Nicholas 


> Message: 6
> Date: Wed, 3 Feb 2010 15:49:34 -0500 (EST)
> From: "Kristen M. Kostelnik" <kristen_kostelnik at ncsu.edu>
> To: r-sig-ecology at r-project.org
> Subject: [R-sig-eco] clumping vs. random
> Message-ID: <54612.98.122.165.51.1265230174.squirrel at webmail.ncsu.edu>
> Content-Type: text/plain;charset=iso-8859-1
> 
> Hello list,
> 
> It seems this should be quite a basic question, but I have no idea how to
> approach it.  For 100s of sites, I have an environmental variable that
> has
> occurences over a 20 year period.  I am looking for a way to create an
> index between 0 and 1 that represents the degree of clumpiness vs.
> randomness over time.  Where 0 is totally clumped and 1 is totally spaced
> out evenly.
> 
> So for example:
> 
> Site     Year1   Year2  Year3   Year4......Year19   Year20    Total  
> Index
> 1         Yes     Yes    Yes     Yes        No        No      10       0
> 2         Yes     No     Yes     No        Yes        No      10       1
> 
> Yes and No can be converted to 1 and 0.  I am not sure what you call this
> sort of index, technically, so I am not sure how to search for an
> appropriate method.  I am, obviously, looking for a way to do this in R.
> 
> Thanks for any suggestions!
> Kind Regards,
> Kristen
> 
> 
> 
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> End of R-sig-ecology Digest, Vol 23, Issue 4
> ********************************************