1. Multilinear Algebra for Analyzing Data with Multiple Linkages Tamara G. Kolda plus: Brett Bader, Danny Dunlavy, Philip Kegelmeyer Sandia National Labs TRICAP 2006, Chania, Greece, June 4-9, 2006

2. Tamara G. Kolda – TRICAP – June 6, 2006 - p.2 Linear Algebra for Data with Linkages Circle-Square Matrix Circle-Circle Co-Link Matrix Square-Square Co-Link Matrix SVD Rank-k Approximation (k=2)

3. Tamara G. Kolda – TRICAP – June 6, 2006 - p.3 Latent Semantic Indexing (LSI) for Text Retrieval S. T. Dumais, G. W. Furnas, T. K. Landauer, S. Deerwester, and R. Harshman. Using latent semantic analysis to improve access to textual information. In CHI '88, pp. 281–285, 1988 S. C. Deerwester, S. T. Dumais, T. K. Landauer, G. W. Furnas, and R. A. Harshman. Indexing by latent semantic analysis. J. Am. Soc. Inform. Sci., 41(6):391–407, 1990 M. W. Berry, S. T. Dumais, and G. W. O'Brien. Using linear algebra for intelligent information retrieval. SIAM Rev., 37(4):573–595, 1995 Term-Document Matrix “Car Service” Query SMART Retrieval System G. Salton (1971) LSI S. Dumais et al. (1988) Terms Documents car repair service military d1 d2 d3

4. Tamara G. Kolda – TRICAP – June 6, 2006 - p.4 Applications of LSI Terms Documents car repair service military d1 d2 d3 Graph the Results using U 2 and V 2 Term-Document Similarities car service military repair d1d2d3 car service military repair carservicemilitaryrepair Term-Term Document-Document

5. Tamara G. Kolda – TRICAP – June 6, 2006 - p.5 Caveats for LSI How to use  Term-document matrix weighting is critical! Local Weight Log f ij = frequency Global Term Weight Inverse Document Frequency N = total docs n i = # docs with term i Normalization Factor “Cosine”

6. Tamara G. Kolda – TRICAP – June 6, 2006 - p.6 Citation/Link Analysis (Same Nodes) 1 2 3 4 Link Matrix Co-Citation Matrix Co-Reference Matrix Hub Scores Authority Scores Doc 3 is the most important authority! Doc 1 is the most important hub! J. M. Kleinberg. Authoritative sources in a hyperlinked environment. J. ACM, 46(5):604–632, 1999. Examples: Citation data, Web links

7. Tamara G. Kolda – TRICAP – June 6, 2006 - p.7 Multiple Links? Suppose the connections between nodes are “labeled” in some fashion. In other words, we have meta-data on the connections. Can we somehow use multilinear algebra for link analysis?

8. Tamara G. Kolda – TRICAP – June 6, 2006 - p.8 PARAFAC PARAFAC = Parallel Factors aka. CANDECOMP = Canonical Decomposition Higher-order analogue of the SVD Columns of A, B, and C are not orthonormal If R is minimal, then R is called the rank of the tensor (Kruskal 1977) Can have rank( X ) > min{ I, J, K } Often guaranteed to be a unique rank decomposition! = A I x R B J x R I x J x K C K x R R x R x R =++ + … I R. A. Harshman. Foundations of the PARAFAC procedure: models and conditions for an “explanatory” multi-modal factor analysis. UCLA working papers in phonetics, 16:1–84, 1970 J. D. Carroll and J. J. Chang. Analysis of individual differences in multidimensional scaling via an N-way generalization of `Eckart-Young' decomposition. Psychometrika, 35:283–319, 1970.

9. Tamara G. Kolda – TRICAP – June 6, 2006 - p.9 Many ways to write PARAFAC J. B. Kruskal. Three-way arrays: rank and uniqueness of trilinear decompositions, with application to arithmetic complexity and statistics. Linear Algebra Appl., 18(2):95–138, 1977. “Kruskal Operator” Easy to write N-way case: “Tucker Operator”

10. Tamara G. Kolda – TRICAP – June 6, 2006 - p.10 Properties of the Kruskal Operator PARAFAC core for a Tucker decomposition: Matricize (arbitrary map of indices to rows and columns): Mode-n matricize: Norm of a PARAFAC decomposition:

11. Tamara G. Kolda – TRICAP – June 6, 2006 - p.11 PARAFAC for sparse data & approximations Our interest in the mathematical operations is motivated on two fronts  (1) Sparse computations  (2) Using tensor decompositions for approximation Ex: Considering how to efficiently implement PARAFAC-ALS for sparse data Can PARAFAC be used for the best rank-k approximation, rather than finding an exact decomposition (excepting noise)  What does it even mean in this case??

12. Tamara G. Kolda – TRICAP – June 6, 2006 - p.12 Multilink Analysis using PARAFAC Quick Review: Tensors for Web Link Analysis  page x page x anchor text (TOPHITS) New work: Tensors for Publication Data Analysis  Case 1: doc x doc x similarity  Case 2: term x doc x author (HO-LSA??)

13. Tamara G. Kolda – TRICAP – June 6, 2006 - p.13 TOPHITS: PARAFAC for Web Link Analysis A set of four hyperlinked web pages Graph representation shows basic connectivity Labeled edges capture context

14. Tamara G. Kolda – TRICAP – June 6, 2006 - p.14 Analyzing Publication Data: Doc x Doc x Similarity Representation

15. Tamara G. Kolda – TRICAP – June 6, 2006 - p.15 Computing Different Doc-Doc Similarities Computing term-based similarities (k=1,2,3) Computing author similarities (k=4) Enforces sparseness! 5022 papers 16617 unique terms (ignoring stop words, words with length less than 3 or greater than 30 characters, and words that appear less than 2 times)  Titles: 5164  Abstracts: 15752  Keywords: 5248 6891 authors 2659 citations

16. Tamara G. Kolda – TRICAP – June 6, 2006 - p.16 PARAFAC for Doc x Doc x Similarity H = “hubs” A = “authorities” C = “connections” Rank-30 decomposition Central idea: Each triplet provides a core “grouping” of the data, i.e., a specific topic.

17. Tamara G. Kolda – TRICAP – June 6, 2006 - p.17 Sample: Grouping 1

18. Tamara G. Kolda – TRICAP – June 6, 2006 - p.18 Sample: Grouping 10

19. Tamara G. Kolda – TRICAP – June 6, 2006 - p.19 Applications of the [ H,A,C ] Decomposition Latent document similarities  Calculate S = ½ HH T + ½ AA T Analyzing a body of work  c h = hub centroid, c a = authority centroid  s = ½ H c h + ½ A c a Disambiguation (EXAMPLE)  Calculate centroids using A (could also use H or A+H)  Calculate simiarlities of centroids Journal predicition  Use matrix A as features for input to a decision tree ensemeble classifier

20. Tamara G. Kolda – TRICAP – June 6, 2006 - p.20 Example of Disambiguation Results Two authors with missing middle initials. 3 possible matches Matrix of Similarities

21. Tamara G. Kolda – TRICAP – June 6, 2006 - p.21 Analyzing Publication Data: Term x Doc x Author Representation term doc author Form tensor X as: Element (i,j,k) is nonzero only if author k wrote document j using term i. 767 documents 2251 terms 1072 authors 59738 nonzeros Terms must appear in at least 3 documents and no more than 10% of all documents. Moreover, it must have at least 2 characters and no more than 30.

22. Tamara G. Kolda – TRICAP – June 6, 2006 - p.22 Different Graph Interpretations for Term x Doc x Author term-doc with author links term-author with doc links author-doc with term links term-doc-author with links Term Doc Different author links represented by different colors

23. Tamara G. Kolda – TRICAP – June 6, 2006 - p.23 Author Data is Too Sparse term doc author Result: Resulting tensor has just a few nonzero columns in each lateral slice. Experimentally, PARAFAC seems to overfit such data and not do a good job of “mixing” different authors.

24. Tamara G. Kolda – TRICAP – June 6, 2006 - p.24 Idea: Use Tucker Transformation to Compress or, equivalently We transform the tensor to a smaller tensor as follows: This transformation forces the authors to be mixed and produces a dense result. Main problem: How to transform sparse tensor without creating dense intermediate results? (rank 75)(rank 50) Compute rank-25 PARAFAC on compressed tensor and transform.

25. Tamara G. Kolda – TRICAP – June 6, 2006 - p.25 Tucker & PARAFAC Want PARAFAC for X in term x doc x author space First, apply dimensionality reduction to X to obtain Y  Y in “conceptual” space Next, compute PARAFAC on Y Finally, reassemble results to yield PARAFAC for X

26. Tamara G. Kolda – TRICAP – June 6, 2006 - p.26 Three-Way Fingerprints Each of the Terms, Docs, and Authors has a rank-k (k=25) fingerprint from the PARAFAC approximation All items can be directly compared in “concept space” Thus, we can compare any of the following  Term-Term  Doc-Doc  Term-Doc  Author-Author  Author-Term  Author-Doc The fingerprints can be used as inputs for clustering, classification, etc.

27. Tamara G. Kolda – TRICAP – June 6, 2006 - p.27 Sample Results: Term

28. Tamara G. Kolda – TRICAP – June 6, 2006 - p.28 Sample Results: Term

29. Tamara G. Kolda – TRICAP – June 6, 2006 - p.29 Sample Results: Author

30. Tamara G. Kolda – TRICAP – June 6, 2006 - p.30 Summary & Future Work PARAFAC provides a technique for analyzing semantic graphs  Third dimension captures different connection types  Or may consider it as the interconnection of 3 different node types Analyzed journal articles using different tensor representations  Doc x Doc x Connection Need to make definitive case of why 3D is better than 2D  Term x Doc x Author Too sparse? Still working towards large-scale, sparse problems  Need implicit compression for PARAFAC  ~5M nonzeros Other decompositions?  Other hybrids  Symmetry

31. Tamara G. Kolda – TRICAP – June 6, 2006 - p.31 Acknowledgments & More Information Thanks to…  Brett Bader, Danny Dunlavy, Philip Kegelmeyer  Web data: Joe Kenny, Travis Bauer et al., Ken Kolda  Journal data: Kevin Boyack  Graph viz: Ann Yoshimura Related papers  Algorithm xxx: MATLAB Tensor Classes for Fast Algorithm Prototyping (with B.W. Bader), ACM TOMS, to appear.  Multilinear algebra for analyzing data with multiple linkages (with D. Dunlavy and W. P. Kegelmeyer), Technical Report SAND2006-2079, Apr. 2006.  Temporal analysis of social networks using three-way DEDICOM (with B.W. Bader and R.Harshman), Technical Report SAND2006-2161, Apr. 2006.  Multilinear operators for higher-order decompositions. Technical Report SAND2006-2081, Apr. 2006.  The TOPHITS model for higher-order web link analysis (with B. Bader), in Proc. Workshop on Link Analysis, Counterterrorism and Security, SDM06, Apr. 2006  Higher-order web link analysis using multilinear algebra (with B.W.Bader), ICDM 2005, pp. 242–249, Nov. 2005. Contact Info:  tgkolda@sandia.gov tgkolda@sandia.gov  http://csmr.ca.sandia.gov/~tgkolda/ http://csmr.ca.sandia.gov/~tgkolda/ Thank You!