Thread: avg() of array values
Hi,
I'm trying to get an avg value of 2 dates (to get to the month that most
part of an interval is in). I found SP's to generate rows from array
values, which I figured I could use with the avg aggregate, but to my
surprise:
*> create or replace function explode_array(in_array anyarray) returns
setof anyelement as
-> $$
$>
$> select ($1)[s] from generate_series(1,array_upper($1, 1)) as s;
$>
$> $$
-> language sql immutable;
CREATE FUNCTION
*> select * from explode_array(array[1, 3]);
explode_array
---------------
1
3
(2 rows)
*> select avg(*) from explode_array(array[1, 3]);
avg
------------------------
1.00000000000000000000
(1 row)
*> select sum(*) from explode_array(array[1, 3]);
sum
-----
2
(1 row)
I would have expected an avg of 2.0 and a sum of 4, where am I going wrong?
Or is there a better way to get the avg of 2 dates (median would
suffice, but I don't know the interval length in days before hand - and
thus not the middle point of the interval).
--
Alban Hertroys
alban@magproductions.nl
magproductions b.v.
T: ++31(0)534346874
F: ++31(0)534346876
M:
I: www.magproductions.nl
A: Postbus 416
7500 AK Enschede
// Integrate Your World //
On Tue, Sep 11, 2007 at 05:50:38PM +0200, Alban Hertroys wrote: > *> select avg(*) from explode_array(array[1, 3]); > avg > ------------------------ > 1.00000000000000000000 > (1 row) avg(*) is not valid, same for sum(*) the reaosn you get the answer you do it because postgres replaces the * with a 1, whic doesn't change the fact that the query is wrong. Have a nice day, -- Martijn van Oosterhout <kleptog@svana.org> http://svana.org/kleptog/ > From each according to his ability. To each according to his ability to litigate.
Attachment
On 9/11/07, Alban Hertroys <alban@magproductions.nl> wrote:
> I would have expected an avg of 2.0 and a sum of 4, where am I going wrong?
This works for me:
select avg(a) from explode_array(array[1, 3]) a;
avg
--------------------
2.0000000000000000
(1 row)
Martijn van Oosterhout wrote: > avg(*) is not valid, same for sum(*) Doh! Thanks. -- Alban Hertroys alban@magproductions.nl magproductions b.v. T: ++31(0)534346874 F: ++31(0)534346876 M: I: www.magproductions.nl A: Postbus 416 7500 AK Enschede // Integrate Your World //