[GRASS-user] Is "i.cluster" an implementation of the ISODATA algorithm?
Markus Neteler
neteler at osgeo.org
Tue Oct 30 01:42:32 PDT 2012
Hi Nikos,
On Tue, Oct 30, 2012 at 7:35 AM, Nikos Alexandris
<nik at nikosalexandris.net> wrote:
...
> 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?
I search in my inbox and found some earlier discussion with the
Subject: "Re: [GRASS-user] Re: algorithm used in i.cluster", see
below.
cheers
Markus
PS: Still we need a text snippet to improve the manual...
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 <georg at muenster.de> 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).
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