NikosA: > > I wonder why the term ISODATA [2] is not to be traced anywhere in the > > GRASS manuals, nor in the GRASS book (3rd ed.). Can someone confirm that > > i.cluster is an(other) implementation of the ISODATA clustering > > algorithm?
MarkusN: > I search in my inbox and found some earlier discussion with the > Subject: "Re: [GRASS-user] Re: algorithm used in i.cluster", see > below. > PS: Still we need a text snippet to improve the manual... Things to keep in mind from the archived discussions (below): - the ISODATA algorithm (Ball and Hall, 1967) is a common modification of the K-means algorithm - the algorithm implemented in the "i.cluster" module involves merging of classes (I_cluster_merge) though no splitting function seems to be implemented Thank you Markus, Nikos --%<--- > On Thu, Apr 22, 2010 at 5:21 PM, Georg Kaspar <georg - muenster.de> wrote: > > Georg Kaspar schrieb: > >> the steps described in > >> http://download.osgeo.org/grass/grass6_progman/c__exec_8c_source.html > >> seem to fit the migrating means algorithm described in richards and jia > >> (2006) and based on the isodata algorithm in ball and hall (1965): > > which is in principle the same as k-means. > > I wrote a mail to Michael Shapiro, who wrote the code back in the 90's and > > received this answer: > >> Georg, > >> It has been a very long time since I wrote that code so my memory may be > >> suspect, but I think that is correct. > On Thu, Apr 22, 2010 at 5:35 PM, Georg Kaspar <[email protected]> wrote: > > Sorry for flooding the list, but i found an interesting note in > > Schowengerdt (2007), p. 400: > > "The ISODATA algorithm (Ball and Hall, 1967) is a common modification of > > the K-means algorithm and includes merging of clusters if their > > separation is below a threshold, and splitting of a single cluster into > > two clusters if it becomes too large" > > The algorithm implemented in the i.cluster module involves merging of > > classes (I_cluster_merge) though no splitting function seems to be > > implemented. > > Since Michael Shapiro stated that he might have used the K-means > > algorithm, I think we can be pretty shure that it is a modified version > > similar to the isodata algorithm, which is described as migrating means in > > Richards (2006). --->%-- _______________________________________________ grass-user mailing list [email protected] http://lists.osgeo.org/mailman/listinfo/grass-user
