Sorry, but it still doesn't work for me. I'm surprised you could get passed the first line, since "projs" is not an argument to raster - it's not necessary for your example to have that set though, so I ignore it.
I had to install igraph package as well, but still this fails at the gridDistance line. Can you let us know your OS, R and package versions for raster, sp, and igraph? Use sessionInfo() please. library(raster) library(sp) library(igraph) rst <- raster(nrow = 200, ncol = 200, xmn = -100, xmx = 100, ymn = -100, ymx = 100) sample.matrix <- t(matrix(c(50,-50, 50,50, -50,50, -50,-50), 2, 4)) sample.matrix <- rbind(sample.matrix, sample.matrix[1,]) sq.polygon <- SpatialPolygons(list(Polygons(list(Polygon(sample.matrix)), ID = "effect_dist"))) rst[] <- runif(ncell(rst)) xy <- matrix(c(0,0), 1, 2) rst.poly <- polygonsToRaster(sq.polygon, rst) rst.lines <- linesToRaster(sq.polygon, rst) rst.lines[rst.lines > 0] <- 0 rst.point <- pointsToRaster(rst, xy) rst.cover <- cover(rst.point, rst.lines) ## fails at this line rst.grid <- gridDistance(rst.cover) rst.grid[!is.na(rst.lines)] <- NA plot(rst.grid) sessionInfo() R version 2.11.1 (2010-05-31) x86_64-pc-mingw32 locale: [1] LC_COLLATE=English_Australia.1252 LC_CTYPE=English_Australia.1252 LC_MONETARY=English_Australia.1252 [4] LC_NUMERIC=C LC_TIME=English_Australia.1252 attached base packages: [1] stats graphics grDevices utils datasets methods base other attached packages: [1] igraph_0.5.3 raster_1.1.7 sp_0.9-64 loaded via a namespace (and not attached): [1] grid_2.11.1 lattice_0.18-8 tools_2.11.1 On Tue, Jun 22, 2010 at 6:28 PM, Roman Luštrik <roman.lust...@gmail.com> wrote: > Thank you Michael for taking interest in my problem. Here is the code that > should work. The only difference is that here, for a polygon, I use a square > instead of a circle (no biggie). I suspect gridDistance may have something > to do with the "hexagon". > > library(raster) > library(sp) > rst <- raster(nrow = 200, ncol = 200, xmn = -100, xmx = 100, ymn = -100, ymx > = 100, projs = "+proj=NA") > sample.matrix <- t(matrix(c(50,-50, 50,50, -50,50, -50,-50), 2, 4)) > sample.matrix <- rbind(sample.matrix, sample.matrix[1,]) > sq.polygon <- SpatialPolygons(list(Polygons(list(Polygon(sample.matrix)), ID > = "effect_dist"))) > rst[] <- runif(ncell(rst)) > xy <- matrix(c(0,0), 1, 2) > > rst.poly <- polygonsToRaster(sq.polygon, rst) > rst.lines <- linesToRaster(sq.polygon, rst) > > rst.lines[rst.lines > 0] <- 0 > rst.point <- pointsToRaster(rst, xy) > > rst.cover <- cover(rst.point, rst.lines) > rst.grid <- gridDistance(rst.cover) > rst.grid[!is.na(rst.lines)] <- NA > plot(rst.grid) > > > Cheers, > Roman > > > > > On Tue, Jun 22, 2010 at 9:55 AM, Michael Sumner <mdsum...@gmail.com> wrote: > >> Could you please provide a reproducible example with useable code? >> >> Cheers, Mike. >> >> On Tue, Jun 22, 2010 at 5:36 PM, Roman Luštrik <roman.lust...@gmail.com> >> wrote: >> > Can someone explain to me why values of distances from a point are not in >> a >> > uniform, circle-like fashion, but rather form a hexagon shape (see >> > image<http://imagepaste.nullnetwork.net/viewimage.php?id=1075>)? >> > Here is the code I'm using to produce this plot (kudos to >> > Robert< >> http://r-sig-geo.2731867.n2.nabble.com/assigning-raster-cell-values-based-on-predefined-criteria-td4929775.html#a4929775 >> >). >> > Raster projection is "+projs = NA". >> > >> > rst.poly <- polygonsToRaster(circle.polygon, rst) #circle.polygon is the >> > polygon I'm overlaying, rst is the raster >> > rst.lines <- linesToRaster(circle.polygon, rst) >> > rst.lines[rst.lines > 0] <- 0 >> > rst.point <- pointsToRaster(rst, xy[[i]][j,]) #xy is the point from where >> > the distances are calculated >> > rst.cover <- cover(rst.point, rst.lines) >> > rst.grid <- gridDistance(rst.cover) >> > rst.grid[!is.na(rst.lines)] <- NA >> > plot(rst.grid) >> > >> > >> > Cheers, >> > Roman >> > >> > >> > -- >> > In God we trust, all others bring data. >> > >> > [[alternative HTML version deleted]] >> > >> > _______________________________________________ >> > R-sig-Geo mailing list >> > R-sig-Geo@stat.math.ethz.ch >> > https://stat.ethz.ch/mailman/listinfo/r-sig-geo >> > >> > > > > -- > In God we trust, all others bring data. > > > > -- > In God we trust, all others bring data. > > [[alternative HTML version deleted]] > > > _______________________________________________ > R-sig-Geo mailing list > R-sig-Geo@stat.math.ethz.ch > https://stat.ethz.ch/mailman/listinfo/r-sig-geo > > _______________________________________________ R-sig-Geo mailing list R-sig-Geo@stat.math.ethz.ch https://stat.ethz.ch/mailman/listinfo/r-sig-geo
