[mlpack-svn] [MLPACK] #355: kernelPCA centering

MLPACK Trac trac at coffeetalk-1.cc.gatech.edu
Thu Jun 26 10:26:40 EDT 2014

#355: kernelPCA centering
 Reporter:  Niteloser  |        Owner:     
     Type:  defect     |       Status:  new
 Priority:  major      |    Milestone:     
Component:  mlpack     |     Keywords:     
 Blocking:             |   Blocked By:     
 I have had a look at the kernelPCA source code. When you centre a kernel
 matrix, should

 arma::sum(kernelMatrix, 1) / kernelMatrix.n_cols;

 not be computed before you subtract the means from the rows in the
 previous line?
 I seem to be getting inconsistent results when using it, with the first PC
 with alternative implementations, but then agreeing from the second PC
 onwards. This seems like a tell-tale sign of centring going wrong.

Ticket URL: <https://trac.research.cc.gatech.edu/fastlab/ticket/355>
MLPACK <www.fast-lab.org>
MLPACK is an intuitive, fast, and scalable C++ machine learning library developed at Georgia Tech.

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