Eamonn O'Brien-Strain

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date: '2004-07-28 18:34:00' layout: post slug: mathematica-eye-candy status: publish title: Mathematica Eye Candy wordpress_id: '33' categories: Programming

[http://obrain.com/~eob/blogPics/historySpace2.gif] I have been working on a little project that involves data mining some personal history. One of the things I have been trying is using principal component analysis to reduce the dimensionality of my data to something I can get an intuitive feel for, so that I can try to ficure out what are the best automated methods for pattern recognition. This image is an example reduced from sixteen variables to three. It's impressive what you can do in Mathematica.

date: '2004-07-27 09:44:54' layout: post slug: applet-demos-of-wolfram-cellular-automota status: publish ref: http://sjsu.rudyrucker.com/nksapplets.htm title: Applet Demos of Wolfram Cellular Automota wordpress_id: '31' categories: Science

Rudy Rucker and his class have done a good job of providing applet versions of some of the cellular automota from Stephen Wolfram's amazing book book “A New Kind of Science”.

I read the book when it first came out. It is nice to be reminded again at how amazing it all is.

date: '2004-07-26 15:31:21' layout: post slug: sdforum status: publish ref: http://www.sdforum.org/SDForum/Templates/Calendar.aspx title: SDForum wordpress_id: '30' categories: Programming

Some interesting technical events sponsored by the SDForum.

I am giving my self a crash course on some data mining techniques for a project I am working on. Here are some things I found useful.

In Matteo Matteucci's site at Politechnico di Milano is a nice little introductory tutorial on clustering algorthms, complete with interactive demos. A similar page is Tariq Rashid's University of Bristol page

Also François Labelle at McGill has a nice overview of reducing the dimensionality of multivariate data using Principal Component Analysis, also with interactive demos which give a nice intuitive feel for the technique. Mathematica supports principal component analysis, so given a data matrix with the each observation in a row, and each column a dimension I found could do the following to get a nice two dimensional view of the multi-dimensional data:

    <<Statistics`MultiDescriptiveStatistics`
    rotated = PrincipalComponents[Transpose[data]];
    rotated2d = Table[ {rotated〚i,1〛, rotated〚i,2〛}, {i,1,n}];
    ListPlot[rotated2d]

date: '2004-07-20 16:53:38' layout: post slug: whale-watching status: publish title: Whale watching wordpress_id: '28' categories: Travel

Just back from an amazing whale-watching boat trip on the straits between San Juan Island, Washington State and Vancouver Island, British Columbia. We were lucky in that all of the local pods of Orca had come together to socialize and hunt for the salmon sheltering from the strong ebb tide currents in coves along the coast. We saw lots of the orca swimming along in family groups, splashing about as they herded the salmon, and popping their heads out of the water to keep an eye on the boats.

Interesting. I think I might be able to use this in my “personal data mining” experiments.

Update 2019-09-14: This code is now on Github at https://github.com/craignm/sequitur

date: '2004-07-06 11:54:37' layout: post slug: memory-footprint-of-java-objects status: publish ref: http://www.javaworld.com/javatips/jw-javatip130_p.html title: Memory footprint of Java Objects. wordpress_id: '26' categories: Programming

A C/C++ programmer, used to using sizeof, might be suprised how hard it is to figure out the memory footprint of Java object. Of course relying on memory sizes is very bad for portability, but sometimes when tuning applications you do need this information.

This article walks through some measurments that reveal:

Object Size (bytes) Overhead (bytes)

Overhead (percent)

Object 8

Integer 16 12 300%

Long 16 8 100 %

int[n] 16 + 4*n

16

char[n] 16 + 2*n 16

String, length n 40 + 2*n 40

date: '2004-07-04 22:27:10' layout: post slug: glimpses-of-the-surface-of-titan status: publish ref: http://photojournal.jpl.nasa.gov/catalog/PIA06407 title: Glimpses of the surface of titan. wordpress_id: '24' categories: Science image: http://photojournal.jpl.nasa.gov/jpeg/PIA06407.jpg image-text: Titan

Finally we are starting to be able to see some detail of Titan's surface through the haze of its atmosphere.

http://photojournal.jpl.nasa.gov/catalog/PIA06407

Screenshot showing Gmail

Got a gmail account a few days ago. So far I like the interface a lot better than yahoo. As is usual with Google it is very clean and uncluttered. So far the targeted ads are unobjectionable, and the “related links” might actually be useful.

date: '2004-06-16 11:30:03' layout: post slug: control-room status: publish ref: http://www.salon.com/ent/feature/2004/06/04/control_room/index_np.html title: Control Room wordpress_id: '22' categories: Society

Last night we saw the film “Control Room”, a behind-the scenes documentary of Al Jazeera covering the initial invasion of Iraq.

I watched some coverage of the war from the Arab side on the Mosaic news program so there was nothing really new factually in this film for me. It was still well worth seeing however as it, for example, demonstrated the complicated realities of how journalists, whether from Fox News or Al Jazeera, unavoidably bring a point of view to their coverage, however committed they are to reporting the “truth”.

One of the compelling characters in the film was a press officer at Central Command whom Salon reports is being muzzled by the Pentagon.