# Compute Buffers Regions `buffer` computes buffers regions from spatial objects belonging to the following classes: `SpatialPoints` (all pixels located within a specified distance of a point take the value one) `SpatialPointsDataFrame` with one column (this column is considered to be a factor, and the buffer is computed for each level of this factor) `SpatialLines` to compute buffers from lines. `SpatialPolygons` to compute buffers from polygons. ```r buffer(xy, x, dist) ``` ## Arguments - `xy`: an object of class `SpatialPoints`, `SpatialPointsDataFrame` with one column (a factor considered to be the identity of the points), `SpatialLines`, or `SpatialPolygons`. - `x`: an object inheriting the class `SpatialPixels` with the same attributes (resolution, size) as those desired for the output. - `dist`: a value of distance ## Returns An object of class `SpatialPixelsDataFrame`. ## Author(s) Clement Calenge clement.calenge@ofb.gouv.fr ## See Also `SpatialPixelsDataFrame-class` for additionnal information on objects of class `SpatialPixelsDataFrame`. ## Examples ```r data(lynxjura) # locs is the SpatialPointsDataFrame containing the # locations of lynx indices in the Jura mountains locs <- lynxjura$locs head(locs) ## just for the sake of illustration: sample 100 points suppressWarnings(RNGversion("3.5.0")) set.seed(233) locs <- locs[sample(1:nrow(locs), 100),] # sa is the SpatialPixelsDataFrame object containing # maps of the study area sa <- lynxjura$map # Buffer of 2000 m from all points bu <- buffer(locs, sa, 2000) image(bu) # displays all the pixels of the study area within 2000 m # of a point, for each type of indices (see ?lynxjura) buani <- buffer(locs[,2], sa, 2000) buani par(mar=c(0,0,2,0)) opar<-par(mfrow=c(3,4)) lapply(1:11, function(i) { image(buani[,i]) title(main = names(slot(buani, "data"))[i]) }) par(opar) ## buffer from a polygon sa2 <- sa[,4] sa2[[1]][sa2[[1]]<5000] <- NA image(sa2) ## gets the contour line gc <- getcontour(sa2) plot(gc, add=TRUE) ## a buffer of 2000 metres image(buffer(gc, sa, 2000)) plot(gc, add=TRUE) ```

buffer function