[R] Creating polygons from scattered points
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 of coastlines etc are maintained. I have spent ages trying to find a package that will allow me to convert scattered point distributions to polygons but haven't found anything that works, the functions I have found 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-help@r-project.org mailing list https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide http://www.R-project.org/posting-guide.html and provide commented, minimal, self-contained, reproducible code.
Re: [R] Creating polygons from scattered points
This might be a question for the R-SIG-Geo or R-SIG-Ecology lists. Best, Michael On Wed, Mar 14, 2012 at 7:13 AM, Louise Mair lm...@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 of coastlines etc are maintained. I have spent ages trying to find a package that will allow me to convert scattered point distributions to polygons but haven't found anything that works, the functions I have found 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-help@r-project.org mailing list https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide http://www.R-project.org/posting-guide.html and provide commented, minimal, self-contained, reproducible code. __ R-help@r-project.org mailing list https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide http://www.R-project.org/posting-guide.html and provide commented, minimal, self-contained, reproducible code.
Re: [R] Creating polygons from scattered points
No time to really think about this, but:
a) to convert scattered point distributions to polygons you might look at
convex hulls; e.g. convhulln {geometry}
b) to identify islands some kind of cluster analysis
Hope that helps a little.
KJ
Louise Mair lm...@york.ac.uk wrote in message
news:camkzt57pep1zkpgm2dg5tn6r0p-_o5tf+wsnurxdohf8zvm...@mail.gmail.com...
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 of coastlines etc are maintained. I
have spent ages trying to find a package that will allow me to convert
scattered point distributions to polygons but haven't found anything that
works, the functions I have found 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]]
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