Tests over the last couple days suggest that r.neighbors may be the, or one of, the causes. We lose most of the artifacts if we turn off smoothing using r.neighbors, and the artifacts are much worse with a neighborhood of 7x7 than 3x3.
We're probably wrong about the date, however. This seems to only show up clearly in very long runs (a simulation of 50 recursive models) and is most pronounced with larger smoothing neighborhoods. Previously we'd done a small neighborhood of 3x3 and done most of our tests for no more than 10 iterations. We only did a couple of long ones and were looking more at stats from the output than the maps themselves. Now we are doing a number of 50+ iteration runs (the most recent one ran for nearly 600 years simulated time). using a median smoother gives much worse results than a mean smoother, though a median ought to be better the larger the neighborhood is, since it should not be affected as much by extreme values. Our next test it to find out if there is some kind of issue with region setting that is interacting with the smoothing. Probably not, but we need to make sure. I'll report more later after. If anyone is interested in seeing what I've tried to describe, I've posted images of the effects of different smoothing parameters at: <http://www.public.asu.edu/~cmbarton/files/LandDyn> Michael On 8/1/07 7:34 PM, "Glynn Clements" <[EMAIL PROTECTED]> wrote: > > Michael Barton wrote: > >> Helena also mentioned r.neighbors as a possible culprit, as I'd forgotten to >> mention that we also use this to smooth results. > > Neither r.neighbors or lib/stats changed during the first half of July. __________________________________________ Michael Barton, Professor of Anthropology Director of Graduate Studies School of Human Evolution & Social Change Center for Social Dynamics & Complexity Arizona State University phone: 480-965-6213 fax: 480-965-7671 www: http://www.public.asu.edu/~cmbarton _______________________________________________ grass-dev mailing list [email protected] http://grass.itc.it/mailman/listinfo/grass-dev
