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Re: nearest neighbor


Chris,

It is an interesing question how to find the nearest neighbor without
computing ALL distances. But I would not be surprised if such a solution
turns out to be slower than computing all distances, e.g. in the
following way. Finding the nearest neighbor from a set of 10^6 points
takes less than 0.4 second on my slow computer here at the university.

p = {2, 1, 3}; 
mat = Array[Random[Real, {0, 4}] & , {10^6, 3}]; 
Extract[mat, Ordering[
    Total[(Transpose[mat] - p)^2], 1]] // Timing

{0.361 Second, {1.97792, 0.982634, 2.98964}}

Regards,

Fred Simons
Eindhoven University of Technology

> -----Original Message-----
> From: Kulp, Chris [mailto:Chris.Kulp at EKU.EDU] 
To: mathgroup at smc.vnet.net
> Subject: [mg66106] [mg66075] nearest neighbor
> 
> 
> Hello:
> 
> I am in interested in finding the nearest neighbor for points 
> in a space whose dimension is greater than two.  How can I do 
> this in Mathematica without computing the distances between 
> all of the points? In particular, I am interested in 
> developing a Mathematica notebook for the false nearest 
> neighbor algorithm used in nonlinear time series analysis.
> 
> 
> 
> 
> Thank you for any help you can give to me.
> 
> 
> 
> Chris Kulp
> 
> 
> 
> Dr. Christopher W. Kulp, Ph.D.
> 
> Assistant Professor of Physics
> 
> Eastern Kentucky University
> 
> Moore 351
> 
> 521 Lancaster Ave.
> 
> Richmond, KY 40475
> 
> 859.622.1528
> 
> chris.kulp at eku.edu
> 
> http://people.eku.edu/kulpc
> 
> 
> 
> 


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