DM: PC plots

[Warren Sarle]

Ronny Kohavi writes:
> I met with him last year and posed the same question of how to
> visualize 10,000 rules to a user.  He did not have a simple answer
> (nor do I expect one).
> 
> As much as I find the area of parallel coordinates fascinating, it
> takes users a long time to understand what is in the scene.  That's
> one reason why there's a 3-month course at Tel-Aviv univ on this
> topic.  There's beautiful theory behind it (e.g., how to pick the
> order), but I don't see it becoming mainstream visualization for 
>data
> mining/viz.  IMHO, business users will not easily understand this
> visualization.

There have been many interesting developments in the theoretical 
aspects
of parallel coordinate plots, and I can imagine that it might take a
3-month course to go into the subject in detail.  But the basic idea 
of
a parallel coordinate plot is very easy to understand.  Researchers 
and
practitioners in clinical psychology, education, and other fields have
used simple parallel coordinate plots for decades, but they call these
plots "profiles". To be more precise, a "profile" is a plot of a 
single
case using parallel coordinates.

Recent advances in computer graphics have made it possible to put
dozens or perhaps hundreds of profiles in a single plot. A plot of
hundreds of profiles can indeed be confusing. But I think even a
"business user" could easily understand a plot showing 1 or 2 
profiles,
and then work up to plots with more numerous profiles.

Displaying and understanding 10,000 profiles is, as Ronny suggests,
quite a challenge.

References:

   Greenhouse, S.W., and Geisser, S. (1959), "On methods in the
   analysis of profile data," Psychometrika, 24, 95-112.

   Hartigan, J.A. (1975), Clustering Algorithms, New York: John
   Wiley & Sons, Inc.

-- 

Warren S. Sarle       SAS Institute Inc.   The opinions expressed here
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