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Re: Multi-Dimensional Histograms

From: Joshua Tolley <eggyknap(at)gmail(dot)com>
To: Robert Haas <robertmhaas(at)gmail(dot)com>
Cc: Nathan Boley <npboley(at)gmail(dot)com>, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>,David Fetter <david(at)fetter(dot)org>,PG Hackers <pgsql-hackers(at)postgresql(dot)org>
Subject: Re: Multi-Dimensional Histograms
Date: 2009-06-30 04:34:22
Message-ID: 20090630043422.GI25336@eddie (view raw or flat)
Thread:
Lists: pgsql-hackers
On Mon, Jun 29, 2009 at 10:22:15PM -0400, Robert Haas wrote:
> I'm finding myself unable to follow all the terminology on this thead.
>  What's dimension reduction? 

For instance, ask a bunch of people a bunch of survey questions, in hopes of
predicting some value (for instance, whether or not these people will
die of a heart attack in the next three years). After waiting three years,
discover that some of the questions didn't really help you predict the
outcome. Remove them from the dataset. That's dimension reduction.

> What's PCA?

Principal Component Analysis,
http://en.wikipedia.org/wiki/Principal_components_analysis

--
Josh / eggyknap
End Point, Corp.
http://www.endpoint.com

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