Hi Kevin, Thank you very much for your email and time. I appreciate it greatly, I worked with gDifference from rgeos, also suggested by Alex. It works fine but it gives you SpatialPolygons instead of SpatialPolygonsDataFrame. In addition to that the row.names are lost which add to complexity in matching and attaching the original data.
I figured out another way:- as my goal was to get information from different rings at different distances. therefore, I counted the number of points in one ring and substracted the number from the lower buffer--gave me exclusive numbers for a ring. The column I got, was then used to do some arithmetics and results came out fine. this is bit simpler (but took me longer to figure this out). Cheers, Vikram. On Tue, Jul 2, 2013 at 3:53 PM, Kevin Cazelles <kevin.cazel...@gmail.com> wrote: > Hi Vikram, > > > I am not sure this will help, but if the main issue is the overlap, try to > use "gDiff". > Here a complete example (I use locator(), to generate points, you just have > to click on the plot !) : > > #------------------------------ > library(rgeos) > #------------------------------ > plot(c(-10,10),c(-10,10), col=0, main="Points", xlab="", ylab="Latitude > (°)") > nbp <- 3 > coordpt <- locator(nbp) > datapt <- runif(nbp, 1,4) > points(coordpt, col=1, pch=20) > #------------------------------ > ptsp <- SpatialPoints(cbind(coordpt$x, coordpt$y), > proj4string=CRS("+proj=longlat +datum=WGS84 +no_defs +ellps=WGS84 > +towgs84=0,0,0")) > #------------------------------ > > Diff1 <- gDifference(gBuffer(ptsp, width=2), gBuffer(ptsp, width=1.7)) > Diff2 <- gDifference(gBuffer(ptsp, width=1.5), gBuffer(ptsp, width=1.2)) > Diff3 <- gDifference(gBuffer(ptsp, width=1), gBuffer(ptsp, width=0.5)) > > plot(Diff1, add=T, col=3) > plot(Diff2, add=T, col=7) > plot(Diff3, add=T, col=2) > > > Have a nice day ! > > > > ===================================== > Kevin Cazelles > kevin.cazel...@gmail.com > Pdh Student > Institut des Sciences de Montpellier (ISEM) > Université du Quebec à Rimouski (UQAR) > > > "On n'est jamais trop vieux pour grandir." > > € € > €€ €€ > €€ €€ > €€€ ________ €€€ > €€€ $$$ $$$ €€€ > €€€ ___ ___ €€€ > < ¥ €€€ _____ €€€ ¥ > > < ¥___€€€ €€€___ ¥ > > < ¥ ==== €€ €€ ==== ¥ > > < ¥ / \ €€ €€ / \ ¥ > > < ¥ | @ | €€ /\ €€ | @ | ¥ > > < ¥ \ __ / €€ / _\ €€ \ __ / ¥ > > < ¥ €€ \ / €€ ¥ > > < ¥¥¥¥¥ __ \/ __ ¥¥¥¥¥ > > $$$ +++ +++ $$$ > $$_____________$$ > > > > > > > > > > _______________________________________________ R-sig-Geo mailing list R-sig-Geo@r-project.org https://stat.ethz.ch/mailman/listinfo/r-sig-geo