On Sun, Sep 21, 2014 at 11:10:41PM +0200, Budulinku Dejmihrasku wrote:

Niels Thanks for the quick response however

http://en.wikipedia.org/wiki/Median

The Median in MonetDB is mapped to Quantile(0.5) which doesn't have any mean of the middle values. http://en.wikipedia.org/wiki/Quantile Niels

and quote:

"If there is an even number of observations, then there is no single middle value; the median is then usually defined to be the mean of the two middle values ^[1] ^[2] (the median of {3, 5, 7, 9} is (5 + 7) / 2 = 6)...."

so by this definition median of {1,2} should return 1.5 running this in Oracle, MSExcel, etc. i get 1.5 as well

if i miss something, or the definition of the Median is different in MonetDB - please let me know thanks in advance milan

On 21. 9. 2014 21:22, Niels Nes wrote:

On Sun, Sep 21, 2014 at 08:33:08PM +0200, Budulinku Dejmihrasku wrote:

Hi, just a quick question regarding to MEDIAN:

with x as (select 1.0 as a union all select 2.0 as a) select sys.median(a) as result from x

returns result=1 i would expect result=1.5 though

1.5 is not a value in the input. Median should always return a value from the input.

Niels

any suggestion? thanks milan

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-- Niels Nes, Centrum Wiskunde & Informatica (CWI) Science Park 123, 1098 XG Amsterdam, The Netherlands room L3.14, phone ++31 20 592-4098 sip:4098@sip.cwi.nl url: http://www.cwi.nl/~niels e-mail: Niels.Nes@cwi.nl

To achieve happiness, you can create your own UDF! Lefteris On Mon, Sep 22, 2014 at 8:29 AM, Budulinku Dejmihrasku < budulinku.dejmihrasku@gmail.com> wrote:

not happy but thanks for the explanation m.

On 22. 9. 2014 7:58, Niels Nes wrote:

...

The Median in MonetDB is mapped to Quantile(0.5) which doesn't have any mean of the middle values.

http://en.wikipedia.org/wiki/Quantile

Niels

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cool - thanks! On 26. 9. 2014 14:19, martin van dinther wrote:

Hi,

maybe this helps:

CREATE AGGREGATE Rmedian(arg1 double) RETURNS double LANGUAGE R { quantile(arg1, 0.5) };

SELECT median(val), Rmedian(val) FROM (SELECT 1.0 as val UNION ALL SELECT 2.0) as virttable;

This returns: 1 for the median() and 1.5 for the Rmedian() set functions.

To use the: LANGUAGE R { quantile(arg1, 0.5) } functionality you will need to use: - the latest MonetDB developer built and - start the mserver5 with option: --set embedded_r=true

Regards, Martin van Dinther

On 22-09-14 08:58, Lefteris wrote:

...

To achieve happiness, you can create your own UDF!

Lefteris

On Mon, Sep 22, 2014 at 8:29 AM, Budulinku Dejmihrasku mailto:budulinku.dejmihrasku@gmail.com> wrote:

not happy but thanks for the explanation m.

On 22. 9. 2014 7:58, Niels Nes wrote:

The Median in MonetDB is mapped to Quantile(0.5) which doesn't have any mean of the middle values.

http://en.wikipedia.org/wiki/Quantile

Niels

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