[GRASS-user] Problem with i.cluster

[Markus Neteler]

On Wed, Mar 30, 2011 at 6:28 PM, ndekoning <nilsdekoning at hotmail.com> wrote:
> Hello,
>
> I have been trying to do an unsupervised classification of my WorldView2
> satellite image. When I am using i.cluster I receive the following message:
> "ERROR: Illegal value(s) of sample intervals (100,100)".
> These are my settings:
>
> group= mul_utm17n at PERMANENT
> subgroup= utm17_sub
> signaturefile= utm17n_sig
> classes= 11
> sample= 100,100
> iterations= 30
> convergence= 99.9
> separation= 0.0
> minimum pixels= 17

I think that the default "separation=0.0" is suboptimal. Try 0.5.

Here also an older posting:

On Fri, Feb 18, 2011 at 9:05 PM, Ned Horning <horning at amnh.org> wrote:
> . I did manage to get it to run after playing with
> some of the variables. If I used the default values for "sample" and
> "min_size" it worked. Unfortunately the default values are less than ideal.
> I think the main problem is with the "sample" parameter. When I enter
> "sample=5,5" I assume that every fifth pixel from every fifth line is being
> sampled for use in calculating the cluster statistics. This is apparently
> too many samples for i.cluster to handle. If I use "sample=100,100" the
> program works as expected (more or less). I have a feeling that the sample
> array is not able to handle a large number of samples.

Please post your findings so that we can eventually optimize the
default parameters.

Markus