Search Postgresql Archives

Re: how do you write aggregate function

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

 



On Mon, Mar 10, 2008 at 10:01:47AM -0500, Justin wrote:
> i wish that could work  but need to keep track of the individual weights 
> as its a percentage of the total amount of the weight. 

Unless you have a different meaning of weighted average to me, I don't
think you do. AFAIK this would produce exactly the same result as what
your code does:

state_function(state,weight,value)
  state[0] = state[0]+weight
  state[1] = state[1]+weight*value

final_function(state)
  return state[1]/state[0]

The state[0] is the same as your _sumedWeight. Because it's a constant in
the second loop you can do the division after. state[1] is your
_sumedWxV times _sumedWeight.

Have a nice day,
-- 
Martijn van Oosterhout   <kleptog@xxxxxxxxx>   http://svana.org/kleptog/
> Please line up in a tree and maintain the heap invariant while 
> boarding. Thank you for flying nlogn airlines.

Attachment: signature.asc
Description: Digital signature


[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]
[Index of Archives]     [Postgresql Jobs]     [Postgresql Admin]     [Postgresql Performance]     [Linux Clusters]     [PHP Home]     [PHP on Windows]     [Kernel Newbies]     [PHP Classes]     [PHP Books]     [PHP Databases]     [Postgresql & PHP]     [Yosemite]
  Powered by Linux