Dear Barbara,
> A frequent question in bird research is comparing
> distributions of bird populations, e.g., according to
> recoveries in winter. I found no straight-forward way to
> describe and compare spatial distributions in genstat - did I
> overlook something?
I noticed that no one had replied to your query (I don't do
much with the procs in 8.4), but others with more experience are silent,
so I will point you at the help which will hopefully get you started.
The manual section you want is 8.4 "Analysis of spatial point patterns"
(page 878) in the PDF file opened by Help>GenStat Guides>Statistics.
This lists the procedures (some in the Windows version only) which cover
this area, but not the full help on these. The follow section of code
will
give you a printout of the help on these procs and each procs example
code:
TEXT SPROCS; !T(FHAT,FZERO,GHAT,GRCSR,KCSRENVELOPES,KHAT,KLABENVELOPES,
\
KSED,KTORENVELOPES,K12HAT,MSEKERNEL2D,PTAREAPOLYGON,
\
PTGRID,PTINTENSITY,PTKERNEL2D,PTSINPOLYGON)
FOR [NTIMES=NVALUES(SPROCS);INDEX=i]
LIBHELP [PRINT=description,options,parameters,method] SPROCS$[i]
LIBEXAMPLE SPROCS$[i]; EX=Example_Code
PRINT Example_Code; Just=LEFT; F=1
ENDFOR
Note you can use some univariate distributions to test for spatial
aggregration, setting up quadrats say, by counting the number of points
within the quadrats and testing whether this fits a Poisson distribution
(which it should if they are randomly positioned), and then progress
on to fitting some aggregrated distibutions like negative-binomial,
Neyman Type A, Polya-Aeppli, Poisson-log Normal or Poisson-Pascal.
The negative-binomial parameter k gives a measure of the aggregation
and could be analysed between locations etc if you had some sort
of replication.
I hope this helps.
Regards,
David
_________________________________________________________
Dr David Baird, Biometrician EMail: [log in to unmask]
Mail: AgResearch, PO Box 60, Gerald St, Lincoln, NEW ZEALAND
Phone: +64 3 983 3975 Fax: +64 3 983 3946
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