[vtkusers] K-means values

[David Doria]

On Wed, Mar 16, 2011 at 4:07 PM, Sara Rolfe <smrolfe at u.washington.edu> wrote:
>
> Hi David,
>
> It's not a difficult fix, I mainly found it awkward since I thought I was missing something simple.  I understand how it works better now and can certainly implement it this way.  I appreciate your clarification.
>
> Sara

If you recall, I had the same sort of "it feels awkward" issues a
while back. I think the problem is that the suite is very very capable
and able to hand very large and serious problems, but many users just
want the "very basic" functionality ("which points belong to which
cluster?", and "what are the cluster means?"), which is hard to get
at. There are many layers of complexity above that that a user must
understand (i.e. this "Learn" and "Derive" that you mentioned) that
are not concepts in a standard textbook explanation of kmeans
clustering. Providing a "simple" interface to do this "one pass" type
of thing would definitely be a nice addition.

That is, replace:

 kMeansStatistics->SetLearnOption( 1 ); // This is on by default.
 kMeansStatistics->SetMaxNumIterations( 1 );
 vtkTable* tab = vtkTable::SafeDownCast(
kMeansStatistics->GetOutputDataObject( 1 ).GetBlock( 0 ) );
 double xc = tab->GetValueByName( label, "x" ).ToDouble();

with

double mean0[3];
kMeans->GetMean(0,mean0);

See the difference :) ?

David D.