If you have the x,y coordinates of an ellipse, you can create a SpatialPolygons or SpatialPolygonsDataFrame following the example in ?over (package sp).
For sampling, see ?spsample -Don -- Don MacQueen Lawrence Livermore National Laboratory 7000 East Ave., L-627 Livermore, CA 94550 925-423-1062 On 3/10/14 12:19 PM, "Anthony Fischbach" <[email protected]> wrote: >I have estimated location error ellipses generated from a continuous-time >version of the correlated random walk model for animal telemetry data >(see http://cran.r-project.org/web/packages/crawl/index.html, functions: >crwMLE and crwPredict). >>From these error ellipses, I wish to randomly select points. >Toward this end, I have two questions. > >Question 1: Is there a handy function that readily allows creation of >polygons from ellipses? >## toy example >ellipses<-data.frame(x=c(251753, 252966, 254179), > y=c(343394, 343315, 343237), > majorAxis=c(0.0, 2753.5, > 2114.8), > minorAxis=c(0.0, 2754.1, > 2118.0), > angle=c(0,0,0)) ## dataFrame > with Ellipse information > ## in this case the majorAxis > is assumed to lie along the x axis > ## x, y define the >centroid >of the ellipse. >coordinates(ellipses) <- x~y ## cast to a spatialPointsDataFrame >ellipses.poly <- >Wonder.function.that.Makes.spatialPolygons.from.ellipses(ellipses) > >Question 2: I know that there is a handy means to randomly generate >locations from within a SpatialPolygon. Please help me find it. > > > >----- >Tony Fischbach, Wildlife Biologist >Walrus Research Program >Alaska Science Center >U.S. Geological Survey >4210 University Drive >Anchorage, AK 99508-4650 > >[email protected] >http://alaska.usgs.gov/science/biology/walrus >-- >View this message in context: >http://r-sig-geo.2731867.n2.nabble.com/build-polygons-from-ellipses-then-s >ample-points-within-the-polygons-tp7585922.html >Sent from the R-sig-geo mailing list archive at Nabble.com. > >_______________________________________________ >R-sig-Geo mailing list >[email protected] >https://stat.ethz.ch/mailman/listinfo/r-sig-geo _______________________________________________ R-sig-Geo mailing list [email protected] https://stat.ethz.ch/mailman/listinfo/r-sig-geo
