... and adding, perhaps, to what David and Jeff told you: Let ctr = c(ctr.lat, ctr.long) be the center of a bird colony (this can be vectorized for many centers).
Then you need to figure out how much change in latitude and longitude a distance of 500 meters is at that ctr (I think latitudes are easy; it's longitudes that vary in distance depending on where you. But I hasten to add that I ain't an expert). You can approximate this by pretending the latitudes and longitude are perpendicular on a plane unless you are close to the poles.I strongly suspect there are functions in geostatistics and/or ecology packages that do this: search (e.g. web or rseek.org) on "convert distance to latitude and longitude" or similar (this seemed to yield useful results when I tried it). Then apply David's (and Jeff's) suggestions. Cheers, Bert Bert Gunter "The trouble with having an open mind is that people keep coming along and sticking things into it." -- Opus (aka Berkeley Breathed in his "Bloom County" comic strip ) On Fri, Jun 17, 2016 at 10:26 AM, Alice Domalik <adoma...@sfu.ca> wrote: > Hi List, > > I'm working with some bird tracking data, and to filter the data set, I need > to exclude points taken at the colony. > I would like to exclude coordinates from within a 500 meter radius of a point > centered on the colony. > However, as an R novice, I'm not sure how to accomplish this. > > My df looks like this: > > AnimalID Latitude Longitude Datetime > > Any suggestions would be greatly appreciated. > > > [[alternative HTML version deleted]] > > ______________________________________________ > R-help@r-project.org mailing list -- To UNSUBSCRIBE and more, see > 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 -- To UNSUBSCRIBE and more, see 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.
