[SciPy-user] Finding clustered vectors

[Aaron Hoover]

Hi all,

I've got a question maybe some of you can help me with. I have two  
images, one of which is a planar translation of the other, so I know  
it contains some of the same "features" (using this loosely) as the  
first image. I have some different approaches matching features and  
using those results to calculate candidate 2D shift vectors for each  
2 image sequence. Most of the time, those vectors aren't all the same  
due to noise, imperfect matching, features leaving the frame, etc.  
However there are usually at least a few whose dx and dy values are  
very close, while the others are somewhat noisy and relatively  
randomly distributed.

My question is, what's the best way to get those values in that  
cluster? I've tried some very simple statistical methods, but because  
of outliers and things, simply comparing to the mean and/or variance  
hasn't worked too well. Basically, if I *know* there's going to be a  
cluster of at least 2 vectors with nearly the same values how can I  
easily extract those values (or the mean of those values)?

Thanks,
Aaron