From c6fdefc1e5fe1a75b721bd56c18e52b4cc778b50 Mon Sep 17 00:00:00 2001 From: Thomas Herrlin Date: Tue, 16 Jul 2013 22:27:01 +0200 Subject: [PATCH] Fix median filter in cdeftutorial Fixes commit 1198d31 What was described as an median filter was actually an average filter. Sort the 3 values then take the middle of them using POP,EXC,POP. Also uses one less prev() to decrease filter delay. See https://en.wikipedia.org/w/index.php?title=Median_filter&oldid=558817813 Alternative fix is to rename "median" with "average" in the description, but there already is an AVG rpn function for that. --- doc/cdeftutorial.pod | 3 +-- 1 file changed, 1 insertion(+), 2 deletions(-) diff --git a/doc/cdeftutorial.pod b/doc/cdeftutorial.pod index b2016a23..ce7c5bed 100644 --- a/doc/cdeftutorial.pod +++ b/doc/cdeftutorial.pod @@ -852,8 +852,7 @@ You may do some complex data filtering: DEF:var=database.rrd:traffic:AVERAGE CDEF:prev1=PREV(var) CDEF:prev2=PREV(prev1) - CDEF:prev3=PREV(prev2) - CDEF:median=prev1,prev2,prev3,+,+,3,/ + CDEF:median=var,prev1,prev2,3,SORT,POP,EXC,POP LINE3:median#000077:filtered LINE1:prev2#007700:'raw data' -- 2.47.2