Introduction to Information Retrieval
Introduction to Information Retrieval
Introduction to Information Retrieval
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<strong>Introduction</strong> <strong>to</strong> <strong>Information</strong> <strong>Retrieval</strong><br />
Collection frequency vs. Document frequency<br />
word collection frequency document frequency<br />
INSURANCE<br />
TRY<br />
• Collection frequency of t: number of <strong>to</strong>kens of t in the<br />
collection<br />
• Document frequency of t: number of documents t occurs in<br />
• Why these numbers?<br />
10440<br />
10422<br />
• Which word is a better search term (and should get a<br />
higher weight)?<br />
• This example suggests that df (and idf) is better for<br />
weighting than cf (and “icf”).<br />
3997<br />
8760<br />
26
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