Oh sorry, you should leave off the grouping: select stddev(a), stddev(b), stddev(c) from foo; Paul On Wed, Jan 21, 2015 at 10:24 AM, Paul Jungwirth <pj@xxxxxxxxxxxxxxxxxxxxxxxx> wrote: > Hi Pierre, > > Looking at your Excel document I think I misinterpreted, and you are > trying to take the stddev of each column separately (which makes a lot > more sense!). In the case you can say this: > > select id, stddev(a), stddev(b), stddev(c) from foo group by id; > > Paul > > > On Wed, Jan 21, 2015 at 10:15 AM, Paul Jungwirth > <pj@xxxxxxxxxxxxxxxxxxxxxxxx> wrote: >> Hi Pierre, >> >> It looks like you're saying that each row has an id plus three numeric >> columns, and you want the stddev calculated from the three numeric >> columns? In that case you could do this: >> >> create table foo (id integer, a float, b float, c float); >> insert into foo values (1, 2,3,4); >> insert into foo values (2, 2,3,4); >> select id, stddev(x) from (select id, unnest(array[a,b,c]) x from foo) >> bar group by id; >> id | stddev >> ----+-------- >> 1 | 1 >> 2 | 1 >> (2 rows) >> >> But if that's correct, then I think your table is badly structured for >> a relational database. It might be better to have just two columns: an >> id and *one* numeric value. Or perhaps an id and an array of numeric >> values if you really want all values in one row. >> >> At a higher level, if you are really taking the stddev of a sample of >> size 3, you should reconsider applying statistical analysis to your >> problem at all. >> >> I hope this helps! >> >> Paul >> >> >> >> >> >> >> >> >> On Wed, Jan 21, 2015 at 10:09 AM, Raymond O'Donnell <rod@xxxxxx> wrote: >>> On 21/01/2015 18:02, Pierre Hsieh wrote: >>>> Hi Raymond, >>>> >>>> Thanks for your reply. Please see detail as following. Thanks again. >>> >>> Can you describe *in words* what sort of calculation you want to do? >>> >>> Ray. >>> >>> >>> -- >>> Raymond O'Donnell :: Galway :: Ireland >>> rod@xxxxxx >>> >>> >>> -- >>> Sent via pgsql-general mailing list (pgsql-general@xxxxxxxxxxxxxx) >>> To make changes to your subscription: >>> http://www.postgresql.org/mailpref/pgsql-general >> >> >> >> -- >> _________________________________ >> Pulchritudo splendor veritatis. > > > > -- > _________________________________ > Pulchritudo splendor veritatis. -- _________________________________ Pulchritudo splendor veritatis. -- Sent via pgsql-general mailing list (pgsql-general@xxxxxxxxxxxxxx) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-general
