Re: Re: Clsuter analysis wiht IDL

[dw(at)isva.dtu.dk (Dorthe Wildenschild)]

<Craig writes:

<I am by no means a statistics or clusters analysis expert, but
from
<looking at the documentation it seems that both CLUST_WTS and
CLUSTER
<require the n-dimensional *positions* of the data points, and not
an
<intensity map.  It is pretty clear that the cluster functions
are
<based on an unweighted set of scatter-points.  If you want to
use your
<intensity information as a weighting, you may be out of luck.

<Perhaps you could achieve what you desire with this code, which
simply
<finds the non-zero pixels:

wh = where(image GT 0, ct)
if ct EQ 0 then message, 'ERROR: the image is blank!'
x = wh MOD 658      ; form x pixel
positions
y = floor(wh / 658) ; form y pixel positions

xy = transpose([[x],[y]]) ; compute the 2-d scatter positions
weights = clust_wts(xy, n_clusters=3)
etc.

<I haven't tried this, so it may take some tweaking.  Good
luck,
<Craig

I'm such a beginner at this I don't know what the MOD function does? (no
on-line help listing for it)
When trying to transpose, IDL corrects me with 
Arrays are allowed 1 - 8
dimensions

thanks for trying to help!
BTW I'm not a Mr. :-)
D