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