Re: MEDIAN as custom aggregate?

Can't you do something like

select age from ages order by age limit 1 offset (select count(*) from ages)/2;

except you can't nest the select so you'll have to use a variable to hold it...

Make sure it does the right thing when there is an odd number of rows.

I don't understand why you want the median and not some parameters of your assumed distribution (mean and variance, for example) but each to his own...

Allan.

Josh Berkus wrote:

> 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
>
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