Points system
For the tables based on points, the points are worked out as below.
The following formula is used:
( ( ChartSize +1 -
Position ) / 100 ) + ( 2.718 ^ ( -Position / 2) ) * ( 0.9 + ( weeknumber / 52 )
/ 10 )
An explanation of the formula:
( ChartSize +1 - Position ) / 100 )
--- This reverses the chart position and divides it by 100 so we don't end
up with large points when they're all added together.
--- Therefore a #1 position in the top 40 get 0.40 points and a #40
position will get 0.01 points.
( 2.718 ^ ( -Position / 2) )
--- This adds an extra few points to the top positions so they are
weighted more.
--- Therefore a #1 position gets an extra 0.61 points, a #2 gets 0.37, a
#10 gets 0.007. After #10 these values become miniscule.
( 0.9 + ( weeknumber / 52 ) / 10 )
--- The value worked out above is then multiplied by a number that
increases as the year increases. This takes into account the larger sales
at Christmas, and the smaller sales at the beginning of the year.
--- This value increases as the year goes on, but is always around 1.
This PDF file shows the values given
to each position when the chart is made up of 40, 75 and 100 positions.
This points system was first developed and used on
UKMix
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