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NullVoid » 2005 » March NullVoid » 2005 » March

Archive for March, 2005

recommender systems with Collaborative Filtering

Tuesday, March 29th, 2005 -- By ET

The British Magazine Economist has published an interesting article about Collaborative Filtering. This is a well written article giving a light introduction of the status quo of research in CF.

Although there are fairly many systems using CF nowadays to recommend products, there is still much room left for further research. Put it in the simplest form, a recommender system is able to “tell me what I want”. This can be done either through a user-user framwork or item-item framework:


In theory, the item-item framework works better because it does not require constant updating of user preferences. In reality, the sparseness of the data can also help us to avoid doing tedious calculations on a million-row by million-column matrix.

As mentioned in the article Prof. John Canny‘s research helps to protect the privacy and at the same time use the aggregate data for providing recommendations. Although interesting, it is only of a second-order importance. In my opinion, as everyone in the system would only be referred to as an ID, it does not make sense to anonymize it further. (In the end, in order to get the creators create better products, the users need to give feedbacks about the existing products). A first order important problem is one about strategic gaming of the system, it is an important question because as people rely more on the recommendations, it is crucial to provide unbiased recommendations.

Another problem is that “There is no pint in making suggestions any more finely tuned than the variations in an individual’s own opinons”. That means if I rated a movie as 4.5/10, and I could have rated it 3.6/10, because internal to my mind, these scores are not that different, both these scores show that I dislike the movie, but I do not hate it. This randomness of numerical ratings resulted from psychological variations would be as severe a problem as mis-reporting.

Transparent Wall Paper

Monday, March 28th, 2005 -- By ET

It is interesting to see through my laptop’s screen, so I implemented this transparent wall paper.
A webcam is attached to the back of the laptop, and it sends the real-time video behind the laptop to my wall paper, it looks like a seeing-through desktop

How nerdy I am

Tuesday, March 22nd, 2005 -- By ET

I am nerdier than 93% of all people. Are you nerdier? Click here to find out!
I was taken to this website from someone who posted a nerd score of 46. I was curious to find how nerdy I am. So I spend 5 precious minutes to take the quiz, and I found, to my delight, that I have a score of 93, almost twice as high as that guy. This is a percentile score, which means that 93% of people who took this quiz are less nerdy than I am. :-)

Funny about the result page, it says:

Supreme Nerd. Apply for a professorship at MIT now!!!.

Althought not exactly applying for a professorship at MIT, I’m pursuing a professorship at MIT. :-) I guess few others would get such a good suggestion as I just got.

perl CPAN bug fixed

Tuesday, March 8th, 2005 -- By ET

Tried to install a module in perl, but it gave me the following error:
LWP failed with code[400] message[FTP return code 000]

It switched through LWP, wget, lynx, etc. then stopped for no reason.

To fix it, just add one line in /etc/bashrc:

This sends an environment variable to the shell, and avoids FTP timeout.

Virtual Hospital

Tuesday, March 8th, 2005 -- By ET

vh title bar
I came across this website called Virtual Hospital
I find it very informative. Last night, I took my daughter to the emergency room at MGH, we arrived at 5:30pm, and could not get diagosed by a doctor until 8pm (it took 5 minutes), then they kept us waiting for a senior doctor to confirm the result, we waited till 10:30pm. While we were waiting, her symptom went away. It took the senior doctor less than 3 minutes to examine her and gave us a very vague conclusion about what was wrong.

Next time, I’ll just go to the virtual hospital.

open books project

Tuesday, March 8th, 2005 -- By ET

Oreilly.com has a great open books project page. Where I can find very interesting books. Many books are in the format of Safari, that I can click and read on the web. This can be really handy because sometimes it is not worthwhile to buy a whole book just because I might need to check out a few pages in them. we media

This is a book called “We, the Media”, I wanted to get a free version from MIT Spam Conference, here I finally get it free, even better, it is searchable.

Comic Competition

Wednesday, March 2nd, 2005 -- By ET

The Daily Grind Iron Man Challenge is a competition between online comic artists to see who can maintain the longest Monday to Friday update schedule, following a strict set of rules.

Each artist lays $20 USD on the line. The last man left standing takes the entire pot.


Current Pot Value: $1,120 USD.

updated matlab econometrics toolbox

Wednesday, March 2nd, 2005 -- By ET

To my big surprise, James LeSage has updated the spatial econometrics toolbox last month. There are a lot of improvements, just reading through the list of functions implemented is enjoyful.

The unpacked size is 32MB, from what I can see, almost all functions I need have been implemented. This will be a great step for me to switch from SAS to Matlab, just because the superior programming capability and beautiful graphics.

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