Re: how to calculate standard deviation from a table

Are you sur you don't want a moving windows
(stddev on 0 to 50 , then stdev on 1 to 51)
..

If you don't want moving windows your query would look like

DROP TABLE IF EXISTS your_data;
CREATE TABLE your_data AS
SELECT s as gid , random() as your_data_value
FROM generate_series(1,10000) as s ;

SELECT min(gid) as min_gid, max(gid) as max_gid, stddev(your_data_value) as
your_stddev
FROM your_data
GROUP BY (gid-1)/50
ORDER BY min_gid ASC

Please note that "min(gid) as min_gid, max(gid) as max_gid" and "ORDER BY
min_gid ASC" are just there to help you understand the result
Cheers,
Rémi-C

2015-01-22 16:49 GMT+01:00 David G Johnston <david(dot)g(dot)johnston(at)gmail(dot)com>:

> Pierre Hsieh wrote
> > Hi
> >
> > This table just has a column which type is integer. There are one million
> > data in this table. I wanna calculate standard deviation on each 50 data
> > by
> > order. It means SD1 is from data 1 to data 50, SD2 is from data 51 to
> > 100.... Is there anyone who can give me some suggestions? Thanks
> >
> > Pierre
>
> Integer division
>
> David J.
>
>
>
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