Wow, cool. The IF statement solved my problem. will read into the useful ARQ functions. thanks for the help, Andy. :)
Yuhan On Fri, Sep 28, 2012 at 1:18 AM, Andy Seaborne <[email protected]> wrote: > On 28/09/12 02:17, Yuhan Zhang wrote: > >> Hi all, >> >> I'm trying to perform a dot product between two values, and sum them up. >> Here's the query: >> >> select ?v ( sum(?s1 * ?s2) AS ?ss) >> where { >> { >> <http://onescreen.com/video#**2389800<http://onescreen.com/video#2389800>> >> < >> http://onescreen.com/video_**freebase#/american_football<http://onescreen.com/video_freebase#/american_football>> >> ?s1 . ?v < >> http://onescreen.com/video_**freebase#/american_football<http://onescreen.com/video_freebase#/american_football>> >> ?s2 } >> UNION >> { >> <http://onescreen.com/video#**2389800<http://onescreen.com/video#2389800>> >> < >> http://onescreen.com/video_**freebase#/american_football/** >> football_player<http://onescreen.com/video_freebase#/american_football/football_player>> >> ?s1 >> . ?v <http://onescreen.com/video_**freebase#/american_football/** >> football_player<http://onescreen.com/video_freebase#/american_football/football_player> >> > >> ?s2 } >> } group by ?v order by DESC (?ss) limit 100 >> >> >> However, instead of sum(?s1 * ?s2) , I'd like to have something like >> sum(?s1 * min(?s1*?s2) ) , to multiple ?s2 but not more than ?s1. and I >> > > sum(?s1 * min(?s1, ?s2) ) presumably > > > reached syntax error, as min function meant to be used to aggregate across >> columns within one variable. >> >> so, my question is, is this calculation possible to achieve easily from >> sparql? sum(?s1 * min(?s1*?s2) ) ? How should I make this happen? >> >> >> Thank you. >> >> Yuhan >> >> > Two ways: > > 1/ > IF(?s1<?s2, ?s1, ?s2) > > SPARQL IF returns values. > > > 2/ > See > http://jena.apache.org/**documentation/query/library-**function.html<http://jena.apache.org/documentation/query/library-function.html> > > PREFIX afn > <http://jena.hpl.hp.com/ARQ/**function#<http://jena.hpl.hp.com/ARQ/function#> > > > afn:min(?s1, ?s2) > > > MIN is only an aggregation function and you can't directly put aggregation > inside an aggregation because the outer aggregator executes the expression > for each row as it goes along but that expression contains something that > was calculated using every row of the group. You can do it with a subquery. > > Andy > > > -- Yuhan Zhang Senior Software Engineer OneScreen Inc. [email protected] <[email protected]> www.onescreen.com (949) 525-4825 Ext: 177 The information contained in this e-mail is for the exclusive use of the intended recipient(s) and may be confidential, proprietary, and/or legally privileged. Inadvertent disclosure of this message does not constitute a waiver of any privilege. If you receive this message in error, please do not directly or indirectly print, copy, retransmit, disseminate, or otherwise use the information. In addition, please delete this e-mail and all copies and notify the sender.
