Hello Mahout community,
I have an custom ItemSimilarity.
Items can have multiple genre info. And some items do not have genre info
available. This custom similarity uses Jaccard coefficient over two genre sets.
(A intersect B) / (A union B), so its range is 0 to 1.
A is genre set of item1
B is genre set of item2
If one of the items does not have genre info, it returns 0.0.
And user,item,pref triples contains pref values between 0.010416667 to 10.0
I am using GenericItemBasedRecommender with getAllOtherItems method overrided.
I have custom IDRescorer that filters out some items. It does not do rescoring.
When I asked recommedation for a user, i see that top 65 items having the same
estimated preference. Even some results have perfect estimated pref value 10.
Is this normal to have same estimated pref values for so many items?
For example:
top 63 has score of 4.015476
63 to 96 has score of 3.9160492
97 has 3.8527777
98 to 100 has 3.472611
Another question is, TanimotoCoefficientSimilarity never returns Double.NaN for
item similarity. However it does for user similarity. How to choose between 0.0
and Double.NaN? What will be the difference in terms of estimated pref?
Thanks.
