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From Yang <teddyyyy...@gmail.com>
Subject SVD, how are the missing values treated?
Date Wed, 11 Sep 2013 00:48:37 GMT
in the simple equation describing SVD:

A = USV

I guess the original matrix A has to have every value filled, so that
mathematics will be able to carry out the calculation, right?

but the mahout package described here:
https://cwiki.apache.org/confluence/display/MAHOUT/Dimensional+Reduction

https://cwiki.apache.org/confluence/display/MAHOUT/SVD+-+Singular+Value+Decomposition


allows for input to be sparse, so most elements of A are missing values. so
I wonder how mahout takes care of the missing values? this paper:
http://www.dtic.mil/cgi-bin/GetTRDoc?AD=ADA439541
fills missing values with some sort of averages, which sounds rather
arbitrary.


thanks
Yang

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