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Information Retrieval

Information Retrieval. March 17, 2003. Handout #7. Course Information. Instructor: Dragomir R. Radev (radev@si.umich.edu) Office: 3080, West Hall Connector Phone: (734) 615-5225 Office hours: M&F 11-12 Course page: http://tangra.si.umich.edu/~radev/650/

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Information Retrieval

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  1. Information Retrieval March 17, 2003 Handout #7

  2. Course Information • Instructor: Dragomir R. Radev (radev@si.umich.edu) • Office: 3080, West Hall Connector • Phone: (734) 615-5225 • Office hours: M&F 11-12 • Course page: http://tangra.si.umich.edu/~radev/650/ • Class meets on Mondays, 1-4 PM in 409 West Hall

  3. Latent Semantic Indexing

  4. Term matrix normalization D1 D2 D3 D4 D5 D1 D2 D3 D4 D5

  5. SVD: Singular Value Decomposition • A=USVT • This decomposition exists for all matrices, dense or sparse • If A has 5 columns and 3 rows, then U will be 5x5 and V will be 3x3 [Berry and Browne] • In Matlab, use [U,S,V] = svd (A)

  6. Applications of LSI • Dimensionality reduction = identification of hidden (latent) concepts • Query matching in latent space

  7. Useful pointers • http://lsa.colorado.edu • http://lsi.research.telcordia.com/ • http://www.cs.utk.edu/~lsi/ • http://javelina.cet.middlebury.edu/lsa/out/lsa_definition.htm • http://citeseer.nj.nec.com/deerwester90indexing.html • http://www.pcug.org.au/~jdowling/

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