[Thuban-list] first stabs at a "visual" classifier

[Daniel Calvelo]

Hi.

In the attachment you will find a set of files and a patch against what was
the June 20th CVS. They provide the beginnings of a custom classifier. Let me
elaborate.

The patch adds a "Custom breaks" option to the class generator. When selected,
it opens a graphical display of the selected field that includes: a histogram
(a slider controls the number of bins used), a "pointgram" (a point, or rather
a vertical bar for each data value) and a set of triangular markers indicating
breaks. These markers can be deleted (double-click) and added (single-click on
a new location). They represent cut points from which a set of ranges will be
generated.

It's visually awful, and lacks useful tricks like value display, a grid-like
positioning method and true sliding capabilities for the markers, but it gives
good visual clues  for manual classification of field values.

Let me know if it's worth enhancing. In coding it, I found several ways in
which it might become a permanent display for the other classifiers, as a
visual guide, but that would require severe tweaking with the classification
infrastructure.

Cheers,

Daniel.

-- Daniel Calvelo Aros
-- Dirección General de Información Agraria
-- Ministerio de Agricultura del Perú
-- (51-1) 424-9001

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