Wait for Bus or Walk January 24, 2008
Posted by Andre Vellino in Logic.2 comments
Here’s a(small) question to which I’ve always wanted to know the answer: is it more effective to wait for the bus or walk to the next bus stop?
The Globe and Mail informs me that some mathematicians at CalTech have given it some thought. Here’s the abstract to their paper on Arxiv.org:
Justin has to travel a distance of d miles along a bus route. Along this route, there are n bus stops i, each spaced at a distance of d_i from the starting point. At each bus stop, Justin is faced with a choice: to walk or to wait. If he walks on, he can still catch a bus at the next bus stop–but if a bus passes him while he walks, he is almost assured a longer wait.
RecSys 2008 in Lausanne January 17, 2008
Posted by Andre Vellino in Collaborative filtering, Recommender service.add a comment
The second (apparently, now, annual) Recommender Systems Conference will be held in Lausanne, 23-25 October 2008.
I grew up in Geneva and I know this region like the back of my hand, so I feel confident about the following recommendation: if you go to the conference, try to extend your stay by a few days and explore one or other of the most picturesque spots in Europe: the Valais or the Bernesese Oberland. It shouldn’t be too cold yet to do some fall mountain hiking – even just a ride on a mountain train is worth the 1.5 – 3 hour train trips from Lausanne.
Despite the endless flock of tourists, Zermatt and Saas-Fee are two of my favourite places in the Valais: you really feel the spirit of the mountains there. Don’t bother with some of the other famous resorts like Verbier (even for skiing) or Montana-Crans unless you enjoy mountain summer Golf or skyscrapers.
It takes a little longer to get to Interlaken and Wengen (in the canton of Berne) but even if you go there just take the Jungfraujoch mountain train, you won’t have wasted your time (only if the weather is good, naturally.)
One thing I like about both Wengen and Zermatt: they have no automobiles – at least not the kind that use an internal combustion engine.
BioMedExperts January 13, 2008
Posted by Andre Vellino in CISTI Visualization, Citation, Information retrieval, Recommender, Search, Social networks.add a comment
Whatever “social networking site for scientists” means exactly, I’m not sure, but whatever it is, it comes in many flavours. There’s the “Facebook” / “LinkedIn” kind of site like Nature’s with forms, blogs, people with whom to make connections etc. There’s the “Del.icio.ous” / “Connotea”, bookmark-centric kind like Elsevier’s 2collab and there’s the “Google Scholar” type of search-engine, like GoPubMed that has been enhanced with subject-specific capabilities such as MeSH and GeneOntology lexicons to improve relevance and classification. GoPubMed also features the ability to search for authors (e.g. by frequency of publication) and Journal (e.g. by impact factor.)
One of the business analysts at CISTI (Naomi Krym) pointed me to the recent launch of BioMedExperts – a new social networking site for bio-med scientists. It was developed by Collexis (and Dell, which supplied the hardware) and combines large subsets of the functionalities in the above services. You can define your own publishing profile as an author, invite authors to your network, define your academic profile and so forth. Collexis also offers “context sensitive search”, whose search results, like GoPubMed, are driven by biomed ontologies.
What I like most about BioMedExperts is the UI that Collexis has devised to help the user navigate the huge network of authors from a citation network. Here’s what the applet looks like:
The goal of Recommender Systems is sometimes framed as “give me what I want” vs. “give me the tools to explore the space so that I can find what I want”. The Collexis applet does an interesting job of the latter for authors and citations.
However, using this applet for even a few minutes demonstrates the need for automated tools that also “recommend” (in some generic sense) or at least removes or hides irrelevant information. Without some kind of recommendation capability there’s just too much data to display in such a small area: it needs to be condensed somehow. Given the appropriate controls (e.g. the slider bars at the top of the Collexis applet) a recommender system could show you a range between the Top N recommendations and the “long tail” in the space of possible recommendations.
So what are the “appropriate contols” for a recommender? Well, it depends on the space of objects being recommended and the recommender algorithm(s). For authors, for example, one of the slider bars could be the weighting given to the text-content similarity of other authors’ articles. Another slider bar could control the display by the similarity of authors’ citation patterns.
For recommending articles with collaborative filtering – e.g. from implicit ratings from users’ viewing patterns – a slider control could weight the articles that are most similar by usage (in different time windows) or by users’ explicit ratings (e.g. “innovation” / “information” / “authority”.)
We’re still not quite there yet, but I think that something like Collexis’ applet is a promising interface for navigating recommendations.
PageRank for Ranking Journals January 10, 2008
Posted by Andre Vellino in CISTI Visualization, Collaborative filtering, Recommender.5 comments
The latest entry in BioMed Central’s blog points us to an alternative database of journal citation metrics from Spain: SCImago.
It uses 13,000 journals, many from Scopus (one wonders – how did they get the IP rights to use the citation data?!)
Like EigenFactor, SCImago performs Journal Ranking using a PageRank-like algorithm.
SCImago also has a nice graphing tool that allows you to look at co-citations maps by subject:
and citation frequency bubble-charts:
by topic and by country for a given year.
It wouldn’t take much to animate sequences of these bubble-maps and show how citation numbers are changing over time, a bit the way Gapminder does it.
In the rankings by country over the past 10 years, Canada article citation ranking is consistently 7th by absolute numbers. On a per capita basis Canada is 6th in cited publications, ahead of the U.S., Germany and France; #1 and #2 per capita are Switzerland and Sweden.
