Dear Louise,
I think there is a couple of possibilities. You might be interested in
clusthr, LoCoH.* and CharHull, also in the package adehabitatHR. Please
check the vignette of the package, section 6:
vignette("adehabitatHR")
In addition, a new estimator could be useful to you as well: the PPA home
range [1]. A R function based on ltraj objects (adehabitatLT) is available
here: http://www.geog.uvic.ca/spar/PPAHomeRange/index.html
Hope this helps,
Mathieu.
[1] Jed A. Long and Trisalyn A. Nelson. 2012. Time geography and wildlife
home range delineation. The Journal of Wildlife Management, 76: 407–413.
DOI: 10.1002/jwmg.259
http://onlinelibrary.wiley.com/doi/10.1002/jwmg.259/abstract
Le 15/03/2012 09:56, Louise Mair a écrit :
Hello,
I have a distribution dataset for species consisting of xy coordinates at
the 1km resolution, with only presence data. So a simplified example of a
species distribution might be:
y<- rbind(as.integer(rnorm(100,50,20)), as.integer(rnorm(200,100,30)),
as.integer(rnorm(100,180,15)))
x<- rbind(as.integer(rnorm(200,50,20)), as.integer(rnorm(200,100,20)),
as.integer(rnorm(100,200,15)))
plot(y~x)
I would like to create polygons for each species distribution, where if an
island is present (as I have tried to show in the example), it would be a
seperate polygon, and the jagged edges where species distributions meet
coastlines etc are maintained. I have tried functions such as mcp in the
package adehabitat, but this produces a very coarse polygon, which doesn't
provide the detailed distribution edges that I need. Other functions I've
tried require the data already to be in the format where the only xy
coordinates present are the outline of the polygon.
Can anyone please recommend a function I can use here, or suggest a way of
extracting the outline points? I have tried this manually but cannot seem
to write a code that will effectively take account of jagged edges and
islands.
Thanks very much for your help,
Louise.
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~$ whoami
Mathieu Basille, Post-Doc
~$ locate
Laboratoire d'Écologie Comportementale et de Conservation de la Faune
+ Centre d'Étude de la Forêt
Département de Biologie
Université Laval, Québec
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http://ase-research.org/basille
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``If you can't win by reason, go for volume.''
Calvin, by Bill Watterson.
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