[GRASSLIST:1853] i.cluster

GRASS GRASS user
1

Why is i.cluster only produsing one class in lover sample as 3,3

Exampel
subgroup: cluster2 = Landsat TM Band 1,2,3,4,5,7

i.cluster group=sachsen subgroup=cluster2 sigfile=sig.25 classes=100 sample=3,3 iterations=30 convergence=98 separation=0 min_size=2

Reading image ... 100%
Iteration 1: %Convergence 2.30 (2m30s elapsed, 35m00s left)
Iteration 2: %Convergence 92.48 (2m40s elapsed, 24m00s left)
Iteration 3: %Convergence 100.00 (2m49s elapsed, 18m18s left)

Sig25 have now only one class why ? I expected it to be 100

It works better white sample=10,10 and sample=20,20

Is it true that i.cluster never create more clusters than the number of start classes ?

Thanks for the help!
/ Maritn Wass
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2

Hi Martin,

On Mon, May 21, 2001 at 02:23:57PM +0000, Martin Wass wrote:

Why is i.cluster only produsing one class in lover sample as 3,3

Exampel
subgroup: cluster2 = Landsat TM Band 1,2,3,4,5,7

i.cluster group=sachsen subgroup=cluster2 sigfile=sig.25 classes=100
sample=3,3 iterations=30 convergence=98 separation=0 min_size=2

Reading image ... 100%
Iteration 1: %Convergence 2.30 (2m30s elapsed, 35m00s left)
Iteration 2: %Convergence 92.48 (2m40s elapsed, 24m00s left)
Iteration 3: %Convergence 100.00 (2m49s elapsed, 18m18s left)

Sig25 have now only one class why ? I expected it to be 100

you provided "100" - this is a theoretical value which might not
be found in your data. So in reality it may be smaller. Assume you
have an image group with everywhere the same value: Even if you
specify class=100 you will get one class only as only one class
is inside the image. So it depends on your data.

It works better white sample=10,10 and sample=20,20

Might be possible, depends on your data.

Is it true that i.cluster never create more clusters than the number of
start classes ?

Yes, I think so.

For "separation" you may try 0.5. "iterations" I wouldn't specify but leave
this to GRASS. "sample" I wouldn't specify.

Thanks for the help!
/ Maritn Wass

You will have to try several parameters as i.cluster only works from
the image statistics. Better results you will get from i.gensigset/i.smap,
an excellent algorithm.

Cheers

Markus

--
Markus Neteler * University of Hannover
Institute of Physical Geography and Landscape Ecology
Schneiderberg 50 * D-30167 Hannover * Germany
Tel: ++49-(0)511-762-4494 Fax: -3984