elaine kuo
2011-May-13 10:27 UTC
[R] to check if a group of values is randomly distributed
Dear list, I have 603 numbers depicting range sizes of birds in Japan. I would like to learn if the 603 range sizes are randomly distributed or not, in order to check if they meet mid-domain effects. Please kindly advise if any R package or function can check the fit. Also, any more references are highly appreciated. Thank you Elaine [[alternative HTML version deleted]]
Steven Kennedy
2011-May-13 10:39 UTC
[R] to check if a group of values is randomly distributed
try the fitdistr() function in the MASS package
Ben Bolker
2011-May-14 01:52 UTC
[R] to check if a group of values is randomly distributed
elaine kuo <elaine.kuo.tw <at> gmail.com> writes:> > Dear list, > > I have 603 numbers depicting range sizes of birds in Japan. > I would like to learn if the 603 range sizes are randomly distributed or > not, in order to check if they meet mid-domain effects. > > Please kindly advise if any R package or function can check the fit. > Also, any more references are highly appreciated. > Thank you >If you are really interested in mid-domain effects in ecology, there is a whole literature on the proper way to do randomization tests -- generally different variants of placing the observed ranges randomly within a specified domain with the constraint that the entire range must fall within the domain, then computing something about the spatial distribution of range densities (i.e. number of coincident ranges at a particular point, or local diversity). I wrote stuff like this for a special case (turtle nesting ranges) a long time ago, but the code is probably several computer systems ago and unretrievable. You might try a query on the r-sig-ecology list. For references, just try searching "mid-domain effect" or "mid-domain hypothesis" -- Colwell and Gotelli have done a lot in this area. Not in R, but googling finds this: <http://viceroy.eeb.uconn.edu/RangeModelPages/MDEReferences.htm> Other than that, "are the range sizes randomly distributed" is a fairly poorly posed question -- they fit *some* distribution. Your question above is different from the typical mid-domain hypothesis question, which is about the arrangement of ranges rather than their distribution of sizes. Ben Bolker