Hi Mark, Is your data on a raster grid? If yes, could it be converted to a vector point set? If you can get it into a vector point set then DBSCAN might solve your problem. The remaining issue is the choice of a cluster validation method to determine the number of clusters. I have developed one that seems to work well for two dimensional data (which is your case), but is still under development. If you have an interest, let me know, I can send code along. Dan
On Tue, 2009-04-14 at 10:26 -0600, Mark Andersen wrote:
Hello, all,
I am currently interested in simulating the initiation and spread of
forest fires in simulated landscapes consisting of 2 tree species (a
native and an invasive). I'm simulating fire seasons of fixed length;
fires can start at any time and in either tree species during this fire
season, and spread through the simulated forest according to a simple
percolation-like process. I have developed the algorithms for this in
Matlab, and don't anticipate any problems converting them to R if I need
to.
However, it's the next task that has me at a loss. At the end of each
fire season, there will be several burned patches on the simulated
landscape; the number of these patches won't necessarily correspond to
the total number of fires that season, because fires may coalesce. I
need to count how many of these burned patches there are, and find the
size of each. It seems that there should be an algorithm available to do
this, but I haven't found one, possibly because I haven't been using the
right search criteria. I used RSiteSearch("spatial cluster"), and got
many references to the spatclus package. However, from the spatclus
documentation it appears that this is not quite what I'm looking for.
Spatclus looks like it picks out potential clusters of occurrence of
some phenomenon (such as earthqukes or cancer); I need something that
will delineate clusters of contiguous pixels with the same value (i.e.,
burned in my simulations). Could anyone point me towards such an
algorithm, or help me get started finding one?
Dan Putler Sauder School of Business University of British Columbia