[Thuban-list] visual classifier

Daniel Calvelo dcalvelo at minag.gob.pe
Thu Dec 4 18:47:00 CET 2003

["Moritz Lennert"]
> When you said:
> > and a set of triangular markers indicating
> > breaks. These markers can be deleted (double-click) and added
> > (single-click on new location). They represent cut points from which a set
> > of ranges will be generated.
> does that mean that these markers are set automatically at the 
> beginning ? How do you define these breaks ?

Yes, they are set initially as evenly spaced. I looked hard at how you could
initialize them using the other classifiers, but the infrastructure ties very
closely the classifiers with the class definitions, and I couldn't find an
elegant, unobtrusive solution.

My idea was to have a permanent View of the classifier (in the cute world, it
would also have visual cues for the corresponding drawing style), in which
markers could be gridded, reset to automatic settings (quantiles, even breaks,
"natural" breaks,...), hand-tuned either visually or by input, and so on. A
kind of classification studio if you wish. Generating the theme classes would
be either a side-effect or an extra action for this subsystem.

I got stuck by wxWindows too. I couldn't produce something correct that gave
me sliders that I could drag and drop. Could wx-savvy people give any hint on

I also explored natural breaks. I found very scarce literature on the subject.
>From what I gathered, natural breaks are based on a kernel approximation to
the data distribution. From previous experience, programming these things
needs tuning and lots of special casing. If you have ideas on the subject,
they are most welcome.


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