Re: nearest neighbor

*To*: mathgroup at smc.vnet.net*Subject*: [mg66184] Re: nearest neighbor*From*: Oliver Ruebenkoenig <ruebenko at uni-freiburg.de>*Date*: Wed, 3 May 2006 02:45:13 -0400 (EDT)*References*: <e2v79h$nm2$1@smc.vnet.net>*Sender*: owner-wri-mathgroup at wolfram.com

Hi, if you would like to find several nearest neighbors then you might want to try a kd-Tree method. You will find the documenation here: http://www.imtek.uni-freiburg.de/simulation/mathematica/IMSweb/imsTOC/Data%20Structures/TreesDocu.html to download follow: http://www.imtek.uni-freiburg.de/simulation/mathematica/IMSweb/ there is also a mailing list: http://elmo.imtek.uni-freiburg.de/mailman/listinfo/ims hth, oliver On Sat, 29 Apr 2006, Simons, F.H. wrote: > 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: [mg66184] 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 > > > > > > > > > > Oliver Ruebenkoenig, <ruebenko at uni-freiburg.de> Phone: ++49 +761 203 7388