K-means clustering, is it possible to get vertical boundaries?

Hello,

I have performed K-means clustering on some data and formed 3 clusters. Here is a graph

http://dl.dropbox.com/u/54057365/All/cluster.JPG

One thing that I notice is that the boundaries between the clusters are horizontal.

In my case, I have a congestion percentage plotted against average velocity. Naturally as the congestion percentage increases the average velocity decrease. However it would be more intuitive if the boundaries were vertical not horizontal.

Is it possible to do this with clustering algorithms?

Sincere thanks

John

Answer 1

[Tom Lane]

I believe the boundaries are horizontal because the scale of the y variable is much larger. Differences in the y direction dominate the measure of the distance between two points. You could simply cluster on the x variable. You could also experiment with clustering on other matrices that adjust the x and y scale:

[x,y/10]   or   [100*x,y]   or ...

and see if you find any of the results appealing.