we went because of the free room and was pleasantly

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Unformatted text preview: tual monopoly JJ NN -2.0! lesser evil RBR JJ -2.3! other problems JJ NNS -2.8! low funds JJ NNS -6.8! unethical prac+ces JJ NNS -8.5! … 64 Average -1.2! Dan Jurafsky Results of Turney algorithm •  410 reviews from Epinions •  170 (41%) nega+ve •  240 (59%) posi+ve •  Majority class baseline: 59% •  Turney algorithm: 74% •  Phrases rather than words •  Learns domain ­specific informa+on 65 Dan Jurafsky Using WordNet to learn polarity S.M. Kim and E. Hovy. 2004. Determining the sen+ment of opinions. COLING 2004 M. Hu and B. Liu. Mining and summarizing customer reviews. In Proceedings of KDD, 2004 •  WordNet: online thesaurus (covered in later lecture). •  Create posi+ve (“good”) and nega+ve seed ­words (“terrible”) •  Find Synonyms and Antonyms •  Posi+ve Set: Add synonyms of posi+ve words (“well”) and antonyms of nega+ve words •  Nega+ve Set: Add synonyms of nega+ve words (“awful”) and antonyms of posi+ve words (”evil”) •  Repeat, following chains of synonyms •  Filter 66 Dan Jurafsky Summary on Learning Lexicons •  Advantages: •  Can be domain ­specific •  Can be more robust (more words) •  Intui+on •  Start with a seed set of words (‘good’, ‘poor’) •  Find other words that have similar polarity: •  Using “and” and “but” •  Using words that occur nearby in the same document •  Using WordNet synonyms and antonyms •  Use seeds and semi ­supervised learning to induce lexicons Sentiment Analysis Learning Sen+ment Lexicons Sentiment Analysis Other Sen+ment Tasks Dan Jurafsky Finding sen%ment of a sentence •  Important for finding aspects or aXributes •  Target of sen+ment •  The food was great but the service was awful! 70 Dan Jurafsky Finding aspect/a;ribute/target of sen%ment M. Hu and B. Liu. 2004. Mining and summarizing customer reviews. In Proceedings of KDD. S. Blair ­Goldensohn, K. Hannan, R. McDonald, T. Neylon, G. Reis, and J. Reynar. 2008. Building a Sen+ment Summarizer for Local Service Reviews. WWW Workshop. •  Frequent phrases + rules •  Find all highly frequent phrases across reviews (“fish tacos”) •  Filter by rules like “occurs right a†er sen+ment word” •  “…great fish tacos” means fish tacos a likely aspect Casino casino, buffet, pool, resort, beds Children’s Barber haircut, job, experience, kids Greek Restaurant food, wine, service, appe+zer, lamb Department Store selec+on, department, sales, shop, clothing Dan Jurafsky Finding aspect/a;ribute/target of sen%ment •  The aspect name may not be in the sentence •  For restau...
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This document was uploaded on 02/14/2014.

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