Step characteristics on raster maps
Perhaps you can do something like r is a Raster* object line is a SpatialLines* object library(raster) rr <- linesToRaster(line, r) rm <- mask(r, rr) crosstab(rm, rr) Robert On Thu, Sep 30, 2010 at 5:46 AM, Mathieu Basille
<basille at ase-research.org> wrote:
Dear list members, I'm trying to compute characteristics along steps (i.e. segments between two points), based on underlying raster maps. The steps originally come from radiotracking data, converted to ltraj objects (adehabitat). The idea is to compute (for example) the habitat composition corresponding to each step instead of each points, as we are interesting in the movement path. I tried different solutions, as I would like to do it with R. I did not find any solution using adehabitat (or the development versions adehabitatMA/LS); 'join' only works for point characteristics, not steps. I also tried using sp and SpatialLinesDataFrame, but overlay does not seem to work with SpatialLines(DataFrame) and SpatialPixelsDataFrame: Error in function (classes, fdef, mtable) ?: ?unable to find an inherited method for function "overlay", for signature "SpatialPixelsDataFrame", "SpatialLinesDataFrame" I also investigated packages raster, trip, and rgeos, without success. Maybe the low level functions of rgeos could be used, but it seems a bit out of my skills (and time available) at the moment. Another solution might be to use spgrass6 in conjunction with GRASS, but I'm not familiar enough with GRASS to judge if it is a viable alternative... I'd welcome any hints/thoughts on this question. Sincerely, Mathieu Basille. -- ~$ whoami Mathieu Basille, Post-Doc ~$ locate Laboratoire d'?cologie Comportementale et de Conservation de la Faune + Centre d'?tude de la For?t D?partement de Biologie Universit? Laval, Qu?bec ~$ info http://ase-research.org/basille ~$ fortune ``If you can't win by reason, go for volume.'' Calvin, by Bill Watterson.
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