Thank you Robert, helpful as always. distance function did the trick. Maybe I should shortly describe my approach to preserve it for posterity. I have a polygon on a raster (with non-polygon cells set to NA). Using function raster::distance, I was able to calculate distance for all NA cells. I set cells with values higher than my desired "buffer range" to NA. I then used this raster as a mask to clip my initial object (this object has values 1:ncell(my.object)).
Cheers, Roman On Thu, Nov 18, 2010 at 3:29 PM, Robert J. Hijmans <r.hijm...@gmail.com>wrote: > Roman, Have you tried combinations of the functions 'edge', and > 'distance' (and perhaps adjacency, if the 'amount' is expressed in > cells rather than distance). Robert > > On Thu, Nov 18, 2010 at 5:58 AM, Roman Luštrik <roman.lust...@gmail.com> > wrote: > > Dear list, > > > > I've been searching around and I continue to do so, but in the mean time > I'm > > seeking your advice on how to improve my approach. > > > > I'm using raster package and I'm trying to find cells around (let's call > it > > a buffer) and inside a polygon. These subsetted cells are used for > > calculations later on. I'm basically trying to "grow" a polygon by a > certain > > specified amount. > > > > I have created a raster with values derived as 1:ncell(my.object), where > > each value actually represents cell number and in a sense, position. This > is > > the playground for my polygon. > > > > So far, I've approached this by: > > - find cell values inside the polygon (former raster::polygonValues) > > - find cell values within the buffer of SpatialLines object (made from > the > > above polygon) (former raster::lineValues) > > - find unique cell values from the above results > > > > The problem is that finding buffers around each cell on a line (second > step) > > is pretty RAM greedy. Would there be a more efficient way of "growing" a > > polygon, preferably without using external software? > > > > > > 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. [[alternative HTML version deleted]]
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