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How to obtain the values of "importance" col. in Shopping Basket results

    Question

  • Fenders         Mountain Bikes        1238     539      43.54%   0.52
    Hydration Packs Bottles and Cages  428     191      44.63%   0.33
    Bike Stands Tires and Tubes           130     103      79.23%   0.26
    Gloves             Helmets                 849     352      41.46%   0.17
    Cleaners       Tires and Tubes         525     259      49.33%   0.05
    Bike Racks Tires and Tubes             191      94      49.21%   0.05
    Helmets         Tires and Tubes      3794   1617      42.62%  -0.02

    Dear Eileen Zhao,
    The above is the shopping basket result on the sample data 'associate'.
    Importance (A => B) = log (p(B|A)/p(B|not A)) <---Please explain the right most col.= Importance (A => B): 0.52, 0.33, 0.26, .....
    Especially how you obtain p(B|not A).

    Thank you.

    PS: Would you explain the difference between 'Itemset' and 'Rule'? What are they?

    MasYam

    Wednesday, May 15, 2013 4:44 PM