RE: Mean/Median

I did a procedure for median some time back. Here is the algorithm that I used.

1. Define a Cursor - Dont forget to use the Order by Column while defining. Ofcourse, U should order by the column on which you need median.
2. Get a count of records that cursor would return ( Regarding How to get a count - U have to define a similar cursor with the same where clause but one that returns count ). Or, simply do a select count into variable.
3. Supposing N is the number of records that the cursor would return,
4. If N is Odd, Then (N/2)+1 th record is the the median record
5. If N is even, then the average of the (N/2) th record and (N/2)+1 the record is the median value of the set.
6. Now Loop thru the cursor until you encounter (N/2)+1 th record and then calculate the median as determined in the steps 4 and 5.

May be I goofed up somewhere - But I am sure my code worked - I checked it against a statistical package ( Cornerstone) generated median.

Correct me if I am wrong.
Rajaram.

-----Original Message-----
From: Tim Sawmiller [SMTP:sawmillert_at_state.mi.us] Sent: Tuesday, May 15, 2001 3:27 PM

To:     Multiple recipients of list ORACLE-L
Subject:        RE: Mean/Median

Well, no, it doesn't work at all. The definition of Median is a value where half your list of values is above, and half is below. If the values all tend toward the mininum or the maximum, this "equation" would be way out of line.

>>> MohanR_at_STARS-SMI.com 05/15/01 01:35PM >>> Oops, this only works for *even* numbers of samples....geez....

|| -----Original Message-----
|| From: Mohan, Ross
|| Sent: Tuesday, May 15, 2001 12:28 PM
|| To: 'ORACLE-L_at_fatcity.com'
|| Subject: RE: Mean/Median
||
||
|| geez louise,
||
|| Median := avg(Max,Min)
||
|| || -----Original Message-----
|| || From: Pat Hildebrand [mailto:pat_at_ssc.upenn.edu]
|| || Sent: Monday, May 14, 2001 10:56 PM
|| || To: Multiple recipients of list ORACLE-L
|| || Subject: Re: Mean/Median
|| ||
|| ||
|| ||
|| || >
|| || > Any scripts (sql or pl/sql) out there to compute various
|| || statistical things
|| || > in Oracle?
|| || >
|| ||
|| || Would depend on just what you are looking for. A quick look at
|| || Oracle's SQL functions showed avg, st. deviation, and variance
|| || although no median but that should be easier to write than
|| || some of the
|| || others.
|| ||
|| || Pat
|| || --
|| || Please see the official ORACLE-L FAQ: http://www.orafaq.com
|| || --
|| || Author: Pat Hildebrand
|| || INET: pat_at_ssc.upenn.edu
|| ||
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