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The Evolution of Treemaps
by Juan C. Dürsteler [message nº 52]

Last week (num 51) we introduced Treemaps and their initial application. Their evolution has gone, however, far beyond that.

On one hand the algorithms have improved their behaviour, ensuring that you don't get hundreds of thin lines and only three or four squares (a technique called squarification) Other algorithms maintain the ordering or allow you a great interactivity with the contents of the Treemap (see the page "Treemap Layout Demonstrations")

On the other hand, although Treemaps began as a solution to visualise a hard disk crammed with data, their applications have begun to bloom in other fields. Let's see some examples.

SmartMoney uses treemaps to visualise more than 500 stocks at the same time, updated every 15 minutes. Each rectangle represents a stock value, whose size represents its market capitalisation. Rectangles are organised by industrial groups and the colour gradation (that you can choose among green-red or blue-yellow for colour blind) depict the level of loses (bright red is -6%) or gain (bright green is +6%). Both colours and sizes are configurable, so they can represent other financial variables.

Hovering the mouse over a rectangle shows you the company, whether their stock price is going up or down, etc. Clicking on a particular rectangle you can access much more detailed information about the stock it represents. But there's much more. This is an excellent and very interesting application worth diving into for a while. The stock exchange at a glance.


Click on the image to see a zoom of it.
PeetsCoffTea.gif (26287 bytes)
Click on the image to see a zoom of it.
SmartMoney's market map. Peet's Coffee and Tea Coffe Selector

Another, perhaps tastier, interesting application is that of Peet's Coffee and Tea. It uses treemaps as a selector of the different coffee brands the company commercialises. In this case rectangles are grouped by coffee type (decaffeinated, Africa-Arabia, etc). The size is proportional to the price and the colour gives an idea of the "body" of the infusion made with that type of bean. Hovering with the mouse makes the coffee label appear and clicking on it you can buy it, get more information or read the opinions of the employees and other customers. Pleasant and intuitive to use.

According to Sami Lais in the article "Treemaps Bloom", which appeared in Computerworld the past July 2nd; last month treemap developers of both sides of the Atlantic gathered to share their research results and it appears that treemaps are beginning to gain momentum.

For example there is a free Java library developed by Christophe Bouthier  a graduate student of LORIA in Nancy, France. It allows you to use the programmed functions to create treemaps to the taste of the programmer, further expanding the possibilities of this visualisation technique.

Whether treemaps will spread or not has to be seen. It's obvious that this is an interesting technique to see both the forest and the trees at a glance in a visually intuitive way. The danger is, in a similar way to what happens with the Kohonen maps (see num_39 of the e-zine), that once the whole and its parts have been seen the map does not offer enough richness in detail and interaction as to give it an intensive use.

The number of applications overcoming this difficulty is increasing, as we have seen with the above mentioned examples.


Links of this issue:

http://www.infovis.net/printMag.php?num=51&lang=2  
http://www.columbia.edu/~mmw111/treemap  
http://www.smartmoney.com/marketmap  
http://www.peets.com/tast/11/coffee_selector.asp  
http://www.computerworld.com/cwi/story/0,1199,NAV47_STO61776,00.html  
http://sourceforge.net/projects/treemap  
http://www.infovis.net/printMag.php?num=39&lang=2  
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