MEDIAN as custom aggregate?

Folks,

Hey, anybody have a custom aggregate for median calucation?  I'm doing
this through a PL/pgSQL function, and a custom aggregate would probably
be faster.

For those whose stats terminology is rusty, the "median" is the "middle"
value in a distribution.  For example, if we had the following data:

Table ages
person        age
Jim        21
Rusty        24
Carol        37
Bob        62
Leah        78

Our Median would be Carol's age, 37.  This is a different figure from
the Mean, or Average, which is 44.4.  Using the combination of the Mean
and the Median you can do all kinds of interesting statistical analysis.

-Josh Berkus


______AGLIO DATABASE SOLUTIONS___________________________                                      Josh Berkus Complete
informationtechnology      josh@agliodbs.com  and data management solutions       (415) 565-7293 for law firms, small
businesses       fax 621-2533   and non-profit organizations.      San Francisco