Re: DM: Clustering and categorical attributes (fwd)

[Warren Sarle]

I wrote:
> There is nothing inherently wrong with doing k-means on dummy 0|1
> variables generated from categorical attributes.

Murray Jorgensen <maj@waikato.ac.nz> replied:
> True, but when dealing with attributes with 1000 levels you would 
>need to
> generate 999 dummy variables for each of these. I see things 
>starting to
> get a little messy!

What's really messy is when people want to use zip codes with 20,000
levels, many of which have only one or two cases. In such situations,
I ask "Do you really want to do that?" and they say "Yes!" <sigh>

But assuming there are adequate data to support the analysis,
generating a few thousand dummy variables isn't all that bad.
It's certainly less hassle than computing a distance matrix when
you have a million cases!

-- 

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