I have looked at R’s src/library/stats/src/Trunmed.c a few times as I wanted something similar too in a standalone C++ class / C subroutine. Note that this are actually two implementations in one, see src/library/stats/man/runmed.Rd (the source of the help file) which says \details{ Apart from the end values, the result \code{y = runmed(x, k)} simply … Read more
In MariaDB / MySQL: SELECT AVG(dd.val) as median_val FROM ( SELECT d.val, @rownum:=@rownum+1 as `row_number`, @total_rows:=@rownum FROM data d, (SELECT @rownum:=0) r WHERE d.val is NOT NULL — put some where clause here ORDER BY d.val ) as dd WHERE dd.row_number IN ( FLOOR((@total_rows+1)/2), FLOOR((@total_rows+2)/2) ); Steve Cohen points out, that after the first pass, … Read more
There are a number of different solutions for finding running median from streamed data, I will briefly talk about them at the very end of the answer. The question is about the details of the a specific solution (max heap/min heap solution), and how heap based solution works is explained below: For the first two … Read more
Python 3.4 has statistics.median: Return the median (middle value) of numeric data. When the number of data points is odd, return the middle data point. When the number of data points is even, the median is interpolated by taking the average of the two middle values: >>> median([1, 3, 5]) 3 >>> median([1, 3, 5, … Read more
If you’re using SQL 2005 or better this is a nice, simple-ish median calculation for a single column in a table: SELECT ( (SELECT MAX(Score) FROM (SELECT TOP 50 PERCENT Score FROM Posts ORDER BY Score) AS BottomHalf) + (SELECT MIN(Score) FROM (SELECT TOP 50 PERCENT Score FROM Posts ORDER BY Score DESC) AS TopHalf) … Read more