Fix average precision at k calculation #54
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This PR fixes #49
According to the Wikipedia page of Average Precision the equation is defined as follow:
where
rel(k)
is an indicator function equaling 1 if the item at rankk
is a relevant document, zero otherwise. Note that the average is over all relevant documents, and the relevant documents not retrieved get a precision score of zero.Before, the average was calculated over the minimum value between the length of the actual value and
k
. This doesn't seem right since the length of the actual list ofk
increases; the AP@K will decrease.I fixed and cleaned up the code. Please consider merging this! This could lead to many mistakes.