Hello - does anyone know the algorithm based on which i.cluster was
written? I am trying out unsupervised classifications by fiddling with
the various parameters specifiable in i.cluster - except that I don't
really understand what they mean. Specifically,
1] How is a cluster determined?i.e. which clustering algorithm is used?
IDRISI uses a "histogram peak technique of cluster analysis" - does GRASS
use this or something different? Any references I can read up as to the
method used?
2] Are the number of initial clusters used before the 1st pass is made
only, or do they count in subsequent passes also?
3] What are the units that the minimum class seperation is to be
specified in - the 4.0 imagery tutorial says that users commonly specify
a value between 0.5 and 1.5 - doesn't make too much sense unless one
knows 0.5 of what- can anyone help?
4] The manual for i.cluster says that both the number of initial clusters
and the min. class seperation will be used to calculate the number of
final clusters - that is why I wanted to know whether the no. of initial
clusters is only used n the clustering alg. before the passes, and the
min. dist used to rearrange pixels subsequently, in each pass. This is
what seemed likely to me, but I would like to have it confirmed by
someone who knows better.....
Sorry, this is a rather "questiony" mail - I hope it isn't too long and
involved.
Thanks a lot for all help
Harini
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| Harini Nagendra E-MAIL : harini@ces.iisc.ernet.in |
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