1 I256: Applied Natural Language Processing Marti Hearst Nov 8, 2006

2 Today Comparing term clustering and category output Clustering in Weka Data mining from blogs

3 LDA Latent Dirchelet Allocation Blei, Ng, Jordan, JLMR 03. LDA is a hierarchical probabilistic model of documents. “LDA allows you to analyze of corpus, and extract the topics that combined to form its documents.” Not really clustering, but in the “soft clustering” ballpark.

4 LDA on Recipes

5 LDA on Recipes

6 CastaNet (Semi)automated facet creation Stoica & Hearst Build up from WordNet Algorithm is fully automatic but we think you can improve results manually afterwards.

7 CastaNet on Recipes

8 CastaNet on Recipes

9 TopicSeek on Enron Technique: pLSI (probabilistic LSI, Hofmann 99) Hand-picked example for website

10 TopicSeek on Medline Technique: pLSI (probabilistic LSI, Hofmann 99) Hand-picked example for website

11 CastaNet on Medline Journal Titles

12 Clustering in Weka

13

14

15

16 Looking at Clustering Results Weka lets you save cluster results to an ARFF file I wrote some python code to process this file and pull out the Subject headings for each newsgroup posting in each cluster.

17 15-way clustering

18

19 Cobweb clustering

20

21 Blog Analysis What’s special about blogs?

22 Blog analysis sites Called blogcount; lots of stats and news about blogs Language, location, marketshare Stats about biggest blogs, demographics Notify when new content posted Trends and recent popular topics

23 Blogs vs. Newsgroups Posting about products … what can we tell? Blog: Newsgroup: Example from Glance, Hurst, and Tomokiyo ‘04

24 Analyzing Blogs for Market Data Figure from Glance, Hurst, Nigam, Siegler, Stockton, & Tomokiyo, KDD’05 Idea: examine comments about a product (or a product’s competition or market) in an automated fashion. Application area: handheld electronic devices.

25 Analyzing Blogs for Market Data Figure from Glance, Hurst, Nigam, Siegler, Stockton, & Tomokiyo, KDD’05

26 Technology used Post segmentation Important phrases Foreground vs. background corpus –Background: text about product –Foreground: certain negative paragraphs about product Sentiment classification What do people talk about when saying negative things about product X? Social network analysis (on discussion boards) What does this group of people talk about when saying negative things about product X? Author dispersion –Many people talking about it, or just a few?

27 Example What common phrases to people use when saying negative things about product X?

28 Example What do people in this group say when saying negative things about product X?

29 Example What do people in this group say when saying negative things about product X?

30 Predicting Film Sales Idea: Use discussion before a film to predict its opening weekend box office scores Use discussion afterwards to predict longer-term sales Separate out topic labels from sentiment labels Outcome: Good predictor for opening weekend, but not for longer term Observation: the nature of discussion gets (and thus harder to analyze) after the film has been out a while. Example from Mishne & Glance, 2006

31 Predicting Film Sales Example from Mishne & Glance, 2006

32 Prediction Film Sales Example from Mishne & Glance, 2006

33 Predicting Film Sales Example from Mishne & Glance, 2006

34 Analyzing Political Blogs Analyze: Who links to whom What the popularity profile looks like –A powerlaw/Zipf/Pareto, of course Look at structure of topic- specific blogs –By #inbound links Image from blogsphere ecosystem via Shirky

35 Analyzing Political Blogs Earlier work examined books bought together in pairs at major retailers Krebs, Divided we Stand??? In other domains the groupings are more distributed.

36

37 from Jan 2003

38 from 2004 election

39 Analyzing Political Blogs Study by Adamic and Glance, 2005 Analyzed 40 most popular political blogs 2 months preceding 2004 US presidential election Also study 1000 political blogs on a one day snapshot Findings for the latter: Liberal and conservative blogs had distinct lists of favorate news sources, people, and topics, with some overlap on current news –Use labels from aggregator sources Linking patterns were indeed pretty internal (91% stayed within political leaning) More and more frequent linking among conservatives –82% conservative linked out vs. 74% of liberal

40 Analyzing Political Blogs For the 40 most popular blogs: Looked for “echo chamber” effect The conservative blogs are more tightly interlinked. Question: do they repeat the same concepts more? –Measured textual similarity among blog posts –Slightly stronger within a political leaning than between, but not one orientation more than the other. Looked for interaction with “mainstream” media Found strong distinctions between which sources cited

41 Image from Adamic & Glance 200

42 Image from Adamic & Glance 200

43 Image from Adamic & Glance 200

44 Image from Adamic & Glance 200

45 Image from Adamic & Glance 200

46 Image from Adamic & Glance 200

47 Next Time Sentiment and Opinion Analysis