[R-sig-Geo] Extracting minimum convex polygons of species distributions

[Anne Ghisla]

On Thu, 15 Mar 2012 10:56:45 -0500
Jaime Burbano Girón <jaimebg27 at gmail.com> wrote:

> Hi Louise, I have calculated minimum convex polygons with "calc_mcp"
> function from package "aspace", but I think this function is not
> longer available, so I attach my script using it, where the function
> is written.
> 
> An other tool that I have used is the Hawth's Analysis Tools
> extension for ArcGIS:
> http://www.spatialecology.com/htools/tooldesc.php

Hawth's tools page states: 

"[Dec 09] HawthsTools is now formally discontinued. The new software
that replaces and improves upon Hawthstools is called the Geospatial
Modelling Environment (http://www.spatialecology.com/gme/index.htm) "

GME uses R in the background but is not (yet) under a open license.

Best,
Anne

> Cheers...
> 
> On Thu, Mar 15, 2012 at 8:56 AM, Louise Mair <lm609 at york.ac.uk> wrote:
> 
> > 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.
> >
> >        [[alternative HTML version deleted]]
> >
> > _______________________________________________
> > R-sig-Geo mailing list
> > R-sig-Geo at r-project.org
> > https://stat.ethz.ch/mailman/listinfo/r-sig-geo
> >
> 
> 
> 



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