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Brian Clarkson’s Life Patterns, Ch 6-7

Brian Clarkson’s Life Patterns, Ch 6-7. cse 574 11 Feb 2004. Situation Classification. Situation = abstract place home, neighborhood, office, store, restaurant, meeting, … “Context free” classification

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Brian Clarkson’s Life Patterns, Ch 6-7

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  1. Brian Clarkson’s Life Patterns, Ch 6-7 cse 574 11 Feb 2004

  2. Situation Classification • Situation = abstract place • home, neighborhood, office, store, restaurant, meeting, … • “Context free” classification • measure similarity between individual 25-frame “chunks”, by calculating log-likelihood of their alignment What’s that? • Good performance within a day, poor between days – 56% vs. 72%

  3. Adding Context • Classification with long-term context • align chunks across 30 days of data • 73% avg. accuracy across different days • Strategy • calculate CF matches • if best match in same day accept, else calculate best long-term match • 85% accuracy

  4. Perplexity • Perplexity – used in speech recognition as a measure of how strongly previous context predicts the next word • Application to Life Patterns: • segment sensor stream • cluster similar segments • create a 1st order Markov model between clusters

  5. Issue: Number of Clusters • How many clusters (situations) to use? • Measuring accuracy (strength) of a model? • compare ground truth at time t against most likely prediction given ground truth for time t-1 • gives simple accuracy / granularity tradeoff • better: mutual information between pairs of adjacent symbols in training data • MI is relative to the particular model • measured in bits

  6. Why do this?

  7. Is Life Complex? • 50% of the time perplexity is < 4 • “A person’s life is not an ever-expanding list of unique situations.” • Is this a statement about life, or about the experimental setup? • What is the role of novelty in the life of any organism?

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