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Top albums, QWR, etc.

Printed From: Progarchives.com
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URL: http://www.progarchives.com/forum/forum_posts.asp?TID=121086
Printed Date: January 23 2022 at 20:13
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Topic: Top albums, QWR, etc.
Posted By: projeKct
Subject: Top albums, QWR, etc.
Date Posted: September 30 2019 at 18:28
Hi there,

I have a math question for you !

Here is the top 3 albums for 2018-2019 as of now :



... and here is the top 3 album for 2017-2018-2019 as of now :



How can IQ be better than All Traps On Earth in one ranking, and All Traps On Earth be better than IQ in another ??

Confused



Replies:
Posted By: patrickq
Date Posted: September 30 2019 at 19:38
apparently QWR is not entirely dependent on average rating and number of votes. I had assumed it was...


Posted By: siLLy puPPy
Date Posted: September 30 2019 at 22:00
I still don't get how the charts work. If you look at the top 250 and scan their positions and then click on a subgenre, the corresponding albums on both charts often don't appear in the same order. Total head scratcher.

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https://rateyourmusic.com/~siLLy_puPPy


Posted By: Gerinski
Date Posted: October 01 2019 at 01:01
The position on the Top Albums list is based on the QWR (Query Weighted Rating) and not on the Average Rating value.

I found this in an older post:

The formula used is:

QWR = (NR + nr) / (N + n)

where QWR is the weighted rating, R is the average rating of all albums (in the selected query), N is the average number of votes per album for all albums (in the selected query), r is the album average and n is the number of ratings of the album.

R and N depend on the filter (i.e. the selected genres and years). So if you add/remove a year or genre to/from your filter then R and N will be recalculated based only on those albums in the filtered set - as a result that changes the QWR values. In other words, removing Heavy Prog changes the values of N and R used in the calculation of QWR and hence used to order the albums. This can have a dramatic effect as albums in the chart can switch places.


Posted By: projeKct
Date Posted: October 01 2019 at 04:15
Originally posted by Gerinski Gerinski wrote:

R and N depend on the filter (i.e. the selected genres and years). So if you add/remove a year or genre to/from your filter then R and N will be recalculated based only on those albums in the filtered set - as a result that changes the QWR values. In other words, removing Heavy Prog changes the values of N and R used in the calculation of QWR and hence used to order the albums. This can have a dramatic effect as albums in the chart can switch places.
"Dramatic" is the word! Thanks for the explanation, but I still believe something must be done to avoid this absurd situation (see first post).


Posted By: Cristi
Date Posted: October 01 2019 at 04:25
is it funny only for me to see users freak out or complain about the front page charts?LOL
Sorry, i could not help it Embarrassed


Posted By: someone_else
Date Posted: October 06 2019 at 15:29
The problem with QWR is that the number that determines the ranking depends on other album rankings in the list, so the rfatings of one album influences the ranking of another.

That's why I always fill in a non-zero minimum average rating value when I look for a list.



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