In R's maptools package, is there a built-in function to test if a given point is "inside" a given polygon on the map? The map was loaded from an ESRI Shapefile. The point's latitude and longitude are known. Thank you! Aleks -- ------------------------ Aleksandr Andreev Fulbright Fellow Graduate School of Management St Petersburg State University
I don't know about the maptools package but one general way to do this would be to compute the convex hull (?chull) of the augmented set of points and test if the point belongs to it. Hope this helps, baptiste On 5 Feb 2009, at 13:21, Aleksandr Andreev wrote:> In R's maptools package, is there a built-in function to test if a > given point is "inside" a given polygon on the map? The map was > loaded from an ESRI Shapefile. The point's latitude and longitude are > known. > > Thank you! > > Aleks > > -- > ------------------------ > Aleksandr Andreev > Fulbright Fellow > Graduate School of Management > St Petersburg State University > > ______________________________________________ > R-help at 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._____________________________ Baptiste Augui? School of Physics University of Exeter Stocker Road, Exeter, Devon, EX4 4QL, UK Phone: +44 1392 264187 http://newton.ex.ac.uk/research/emag
On Thu, Feb 5, 2009 at 3:21 PM, Aleksandr Andreev <aleksandr.andreev at gmail.com> wrote:> In R's maptools package, is there a built-in function to test if a > given point is "inside" a given polygon on the map? The map was > loaded from an ESRI Shapefile. The point's latitude and longitude are > known.If everything else fails, convert the shape file into a raster and "drill down" at the location of the points. Rainer> > Thank you! > > Aleks > > -- > ------------------------ > Aleksandr Andreev > Fulbright Fellow > Graduate School of Management > St Petersburg State University > > ______________________________________________ > R-help at 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. >-- Rainer M. Krug, PhD (Conservation Ecology, SUN), MSc (Conservation Biology, UCT), Dipl. Phys. (Germany) Centre of Excellence for Invasion Biology Faculty of Science Natural Sciences Building Private Bag X1 University of Stellenbosch Matieland 7602 South Africa
Hi, You may want to check the package sp. There is one function called "point.in.polygo" that might do what you want. Good luck, Monica --------------------->Message: 32 >Date: Thu, 5 Feb 2009 14:51:36 +0000 >From: baptiste auguie >Subject: Re: [R] maptools: Test if point is in polygon >To: Aleksandr Andreev >Cc: "r-help at r-project.org" >Message-ID: >Content-Type: text/plain; charset=ISO-8859-1; format=flowed; delsp=yes>I don't know about the maptools package but one general way to do this >would be to compute the convex hull (?chull) of the augmented set of >points and test if the point belongs to it.>Hope this helps,>baptiste>On 5 Feb 2009, at 13:21, Aleksandr Andreev wrote:> In R's maptools package, is there a built-in function to test if a > given point is "inside" a given polygon on the map? The map was > loaded from an ESRI Shapefile. The point's latitude and longitude are > known. > > Thank you! > > Aleks > > -- > ------------------------ > Aleksandr Andreev > Fulbright Fellow > Graduate School of Management > St Petersburg State University