Official: MIC Puerto Rico

Back in April, I mentioned that Microsoft will be co-launching with Interamerican University of Puerto Rico, Metropolitan Campus the Microsoft Innovation Center (MIC) of Puerto Rico.

Well, tomorrow is the official inauguration. the university generously has provided me with lab and office space to start an interesting research project within the MIC building. These are exciting news. I cannot comment much about the project, except to say that it is at the interface of search engines, social networks, and information security.

It looks like I will have my hands full between workig at two universities, blogging, and doing consulting work.

IR Videos in Spanish

I normally do not put online my lecture notes (ppt, pdf, videos). However, there are two public conferences that event organizers taped. Both last over 1 hour and are in Spanish, but with slides in English. Here are the links. The quality of the videos is so-so.

Since the videos were made available few months later after the events, these are not properly dated. I have included below the actual date of the events. If you don’t know Spanish, you are out of luck.

1. Understanding Search Engines (Entendiendo a los Buscadores), University of Puerto Rico, Bayamon, 4-23-2008

http://video.google.com/videoplay?docid=-653964730907023811

This one last for about two hours. The audience consisted of grad students and researchers. Unfortunately, the video has an audio-visual mismatch of about one slide. If you can coupe with this, I hope you like it.

2. Demystifying LSI (Desmitificando LSI)- OJOBuscador Congress, Madrid, Spain, 3-09-2007.

http://www.ojotube.com/videos/congreso-ojobuscador-2007-ponencia-desmitificando-lsi-de-dr-e-garcia/

This one last for over one hour. Since it was for a non-scientific audience  (most Spanish SEOs)  I tried to talk very slow.

What is a Similarity Matrix?

Soon or later CS students, in particularly those in IR, will need to deal with similarity matrices.

In simple terms, any matrix M that exhibits the following five characteristics is a similarity matrix.

Squaredness = M must have the same number of rows and columns.
Non-Negativity = all elements of M must be real, non-negative numbers.
Boundedness = all elements of M must adopt values between 0 and 1.
Reflexivity = all diagonal elements of M (i.e. from left to bottom) must be filled with 1.
Symmetry = all ij elements must be identical to all ji elements.

A matrix that fails to exhibit any of these characteristics is not a similarity matrix.

Accordingly, some matrices found in the literature on LSI and whose elements have been referred to as similarities are not so since the corresponding matrix does not conform to the above definition.

Note. This information will help those that took the IR Quiz on Matrices to realize how well they did.

Computing Co-Occurrence Matrices with Excel

The QA column of the current issue of IR Watch – The Newsletter features the following question:

Question: In Excel, how do you convert a term-document occurrence matrix into a term-term or document-document co-occurrence matrix?

Answer:

Let A be a matrix populated with term occurrences (frequencies).
Let A^T be its transpose.

Then, T = AA^T is a term-term co-occurrence matrix, and D = A^TA is a document-document co-occurrence matrix.

The following table emulates an Excel spreadsheet.

	A	B	C	D
1	A =	d1	d2	d3
2	t1	0	1	0
3	t2	0	0	1
4	t3	1	1	1
5
6	T = AAT	t1	t2	t3
7	t1	1	0	1
8	t2	0	1	1
9	t3	1	1	3
10
11	D = ATA	d1	d2	d3
12	d1	1	1	1
13	d2	1	2	1
14	d3	1	1	2

In the table, T was computed by selecting a destination array, entering in its first empty cell (B7) the formula =MMULT(B2:D4,TRANSPOSE(B2:D4)), pressing the f2 key and then the Ctrl+Shift+Enter keys.

Similarly, D was computed by selecting a destination array, entering in its first empty cell (B12) the formula =MMULT(TRANSPOSE(B2:D4),B2:D4), pressing the f2 key and then the Ctrl+Shift+Enter keys.

That was easy!

Note that none of these are similarity matrices. Can you tell why?

IRW-2009-6:Hackers: Taxonomy & Writing Styles

The current issue of IRW should reach subscribers inbox during the day or at the latest, tomorrow.

In this issue:

• Featuring article: Hackers: Taxonomy and Writing Styles
  Due to the increasing interest in developing Information Retrieval and Data Mining courses at the intersection of Information Security, this issue of the newsletter covers a brief taxonomy on hackers and their writing styles.
• QA: Excel Matrix Multiplications: How to convert a term-document occurrence matrix into a term-term or document-document co-occurrence matrix?
• Vacuum Tubes & Transistors Historical
• Who is Who in IR: Thomas K. Landauer
• Top CS Departments: Dartmouth College
• Outstanding Graduate Theses
• Calls and Events
• IR Blogs
• and more…