lecture18-learning-ranking-handouts-6-per

# 1541 introducontoinformaonretrieval

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Unformatted text preview:  how do we  tell how good our scoring func)on is?  Introduc)on to Informa)on Retrieval Sec. 6.1.2  Introduc)on to Informa)on Retrieval Choosing g  Choosing g    In our simple sesng, all that magers is the number  of examples* of each equivalence class    Deﬁne:    n01r = # examples with sT=0, sB=1, judgment = Rel    n01n = # examples with sT=0, sB=1, judgment = NonRel    n10r = # examples with sT=1, sB=0, judgment = Rel    n10n = # examples with sT=1, sB=0, judgment = NonRel    (and similarly n00r, n00n, n11r and n11n corresponding to  the 4 other equivalence classes)    The n01r examples with sT=0, sB=1 combined  contribute a total least‐squared error of    Similarly, add up the error contribu)ons of the other  3 combina)ons of sT and sB for a total error of  * this may not hold for other sets of features, e.g., the # characters in the query 2 5/30/11 Introduc)on to Informa)on Retrieval Introduc)on to Informa)on Retrieval Choosing g is now elementary calculus  Generalizing this simple example    Diﬀeren)a)ng the total error wrt g we get the  op)mal value for g to be    More (than 2) features    Non‐Boolean fea...
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## This document was uploaded on 02/26/2014.

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