       Re: nearest neighbor

• To: mathgroup at smc.vnet.net
• Subject: [mg66106] Re: [mg66075] nearest neighbor
• From: "Simons, F.H." <F.H.Simons at tue.nl>
• Date: Sat, 29 Apr 2006 03:41:11 -0400 (EDT)
• Sender: owner-wri-mathgroup at wolfram.com

```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.
>
>
>
>
>
>
>
> 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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