Hello, I am sorry to post this question a second time, but I still got no solution. My starting point are the local densities from a kernel density estimation (my object called k1) using the splancs package, now I want to calculate the mean value for every superimposed polygon (called tsids). The example code below should help to reproduce my question.
Any help would be greatly appreciated!!! Thanks and kind regards Marco ----------- library(rgdal); library(splancs); library(sp); library(maptools); library(gpclib) # test data + window study site sids <- readOGR(system.file("shapes/sids.shp", package = "maptools"), "sids") crs <- CRS("+proj=longlat +datum=NAD27") proj4string(sids) <- crs plot(sids) ncrs <- CRS("+proj=utm +zone=18 +datum=NAD27") tsids <- spTransform(sids, ncrs) plot(tsids) win <- unionSpatialPolygons(tsids, rep("x", length(slot(tsids, "polygons")))) proj4string(win) <- ncrs tcoord <- cbind(coordinates(tsids)[,1], coordinates(tsids)[,2]) tpoi <- SpatialPoints(tcoord) proj4string(tpoi) <- ncrs plot(win) plot(tpoi, add=T) # define splancs objects tpoi.pts <- as.points(coordinates(tpoi)) win.pol = as.points(list(x=...@polygons[[1]]@polygons[[...@coords[,1], y=...@polygons[[1]]@polygons[[...@coords[,2])) # define grid, bandwith for kernel density estimation pixs <- 15000 dimx <- ceiling(abs((bbox(win)[1,1] - bbox(win)[1,2])/pixs)) dimy <- ceiling(abs((bbox(win)[2,1] - bbox(win)[2,2])/pixs)) grd <- GridTopology(cellcentre.offset=c(bbox(win)[1,1], bbox(win)[2,1]), cellsize=c(pixs, pixs), cells.dim=c(dimx,dimy)) summary(grd) # kernel density estimation kde <- spkernel2d(tpoi.pts, win.pol, 2000, grd) kdf <- data.frame(k0=kde) k <- SpatialGridDataFrame(grd, data=kdf) spplot(k, sp.layout = list(list("sp.polygons", tsids))) k1 <- as(k, "SpatialPointsDataFrame") k1[["x"]] <- coordinates(k1)[,1] k1[["y"]] <- coordinates(k1)[,2] # the following part shows my problem: how can i aggregate the kernel estimations (using the mean) for every polygon in the tsids object? using the overlay function: overlay(k1, tsids, fn = mean) ? -- Jetzt kostenlos herunterladen: Internet Explorer 8 und Mozilla Firefox 3 - sicherer, schneller und einfacher! http://portal.gmx.net/de/go/chbrowser _______________________________________________ R-sig-Geo mailing list R-sig-Geo@stat.math.ethz.ch https://stat.ethz.ch/mailman/listinfo/r-sig-geo