Interactive Self-Organizing Map demonstrations (in Java)

On these pages you will find two interactive demonstrations of how the Self-Organizing Map algorithm operates. Two demos are provided: the first one demonstrates the SOM algorithm for a one-dimensional map, whereas the second one is a more complex demonstration with many possibilities for experimenting. In both demonstrations you can see the map 'live' as it is being taught. You can also interact with the teaching process either by changing the parameters or by selecting the inputs for the map.

The demonstrations require a Java-capable browser such as Netscape. If you have problems with the demos, see the notes at the end of the page.

First demo - The simplest case

The first demo shows the SOM algorithm in a nutshell. When the self-organizing map algorithm controls a row of sliders, they gradually become ordered when random inputs are presented.

Go to the first demonstration.

Second demo - Visualizing a data set

The second demonstration is more complex. A two-dimensional map is taught with data from four classes. As the result the classes will occupy separate areas on the map. Classes and their proportions as well as other parameters may be set by the user allowing a wide range of experiments.

Go to the second demonstration.


These demos were made by Jussi Hynninen. If you have any comments, send them to

The demos have been tested with the JDK's appletviewer on SGI and Netscape 2.0 on several UNIX platforms (SGI, HPUX, DEC OSF/1, Linux). We've tried them once with Netscape 2.0 for W95 and the display was completely messed up but it might have been an isolated incident. Anyway, We'd like to hear how they work for you.

We have had some problems with the loading of the applets. The demos seem to work best if you first go to the first demo and from there directly to the second using the link provided at the end of the page. If you come from the first demo back to this page (with the BACK-button) and then go to the second demo, things may get stuck. Stopping, reloading, visiting other pages, etc. might finally get the thing loaded.

The demos can also be downloaded as gzipped tar or zip archives. They include all necessary files and also demo sources. Download one of: somdemo.tar.gz or

* Neural Networks Research Centre * Java SOM Demo *

Last modified: Wed Sep 29 20:29:41 1999