Does this get you started? It calculates a running standard deviation over a window. With a bit more effort you can add a running average and other calculations on the window. Do you have a reference for this streakedness measurement? I couldn't find one.
I used this library extension from http://www.sqlite.org/contrib http://www.sqlite.org/contrib/download/extension-functions.c?get=25 Assumes window size of 10 but you could put that value in the data (if it's variable) and use it from there too if you want. FYI...a linear sequence like this has a constant standard deviation. select load_extension('./libsqlitefunctions.so'); create table a(n,deviation); create table window(n); create trigger trig1 after insert on a begin delete from window where rowid%10 = new.rowid%10; insert into window values(new.n); update a set deviation = (select sqrt(sum(square(n-(select sum(n)/10 from window)))/10) from window) where new.rowid >=10 and rowid=new.rowid; end; insert into a(n) values(1.0); insert into a(n) values(2.0); insert into a(n) values(3.0); insert into a(n) values(4.0); insert into a(n) values(5.0); insert into a(n) values(6.0); insert into a(n) values(7.0); insert into a(n) values(8.0); insert into a(n) values(9.0); insert into a(n) values(10.0); insert into a(n) values(11.0); insert into a(n) values(12.0); insert into a(n) values(13.0); insert into a(n) values(14.0); insert into a(n) values(15.0); insert into a(n) values(16.0); insert into a(n) values(17.0); insert into a(n) values(18.0); insert into a(n) values(19.0); insert into a(n) values(20.0); select * from a; 1.0| 2.0| 3.0| 4.0| 5.0| 6.0| 7.0| 8.0| 9.0| 10.0|2.87228132326901 11.0|2.87228132326901 12.0|2.87228132326901 13.0|2.87228132326901 14.0|2.87228132326901 15.0|2.87228132326901 16.0|2.87228132326901 17.0|2.87228132326901 18.0|2.87228132326901 19.0|2.87228132326901 20.0|2.87228132326901 -----Original Message----- From: sqlite-users-boun...@sqlite.org [mailto:sqlite-users-boun...@sqlite.org] On Behalf Of Frank Chang Sent: Monday, February 18, 2013 9:50 AM To: sqlite-users@sqlite.org Subject: [sqlite] Is it possible to use SQLITE to calculate the streakedness of numeric data? Would anyone know how to use SQLITE to calculate the streakedness of data? The definition of streakedness is how many deviations away from the mean(i.e running average a numerical data streak is Thank you for your help. A variable R can be used to indicate how many deviations away from the mean a particular streak is. According to the disclosed embodiment, the level of a streak can be defined not just in (integer*deviation) distances from the mean but also as (integer*fraction_of_deviation) distances. To accomplish this, a variable R-factor can be used. The R-factor indicates the separation between two successive R-levels in terms of a fraction of the deviation. By varying the R-factor, streaks can be ranked as required. However, the "credibility" of the streak should also be considered, and included in a ranking mechanism. The deviation within the streak is an obvious measure of how staggered the data is within the streak. A good streak should be less staggered, or in other words, have less deviation. For this reason, a very high level streak is considered to be good, even if its deviation is more than what would normally be desired. Thus, while the level R influences the ranking positively, the deviation within the streak influences it negatively. _______________________________________________ sqlite-users mailing list sqlite-users@sqlite.org http://sqlite.org:8080/cgi-bin/mailman/listinfo/sqlite-users _______________________________________________ sqlite-users mailing list sqlite-users@sqlite.org http://sqlite.org:8080/cgi-bin/mailman/listinfo/sqlite-users
