Geometric Aspects of LSA
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Geometric Aspects of Semantic IndexingDr. Heinrich Hartmann (Oxford)
WeST Koblenz, 31.08.2012
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Outline
1. Latent Semantic Analysis
2. Geometry of SVD
3. Common Ground
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Part 1Latent Semantic Analysis
Problem. Given a set of documents(D1,...,DN)
which documents have a similar topic?
Answer. Latent Semantic Analysis (Deerwester, et. al. 1990)
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Latent Semantic Analysis - 2
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Latent Semantic Analysis - 3
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Latent Semantic Analysis - 4
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Latent Semantic Analysis - 5
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Part 2Geometry of SVD
Study geometry of the associated map!
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Part 3Common Ground
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Common GroundThe extremal vector
Which meaning has the extremal vector?
Inside the term-space.
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Common GroundExample 1
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Common GroundExample 2
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Common GroundExample 3
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Common GroundConclusion
The extremal vector represents the Dominant Topic.
Thank You