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harms/gist:1624764

Created January 17, 2012 04:47
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J for directionally filtering out rows or columns of a matrix.
Raw
gistfile1.txt
'byRow byColumn'=: <"0 s:' Row Column' NB. these two names may be any two distinct values
nix=: 2 :' #~"(1+n=byRow) -.@ u"(1+n=byColumn) '
NB. examples of use:
(2={.) nix byColumn i. 3 5
0 1 3 4
5 6 8 9
10 11 13 14
(2|+/%#) nix byRow i. 3 5
0 1 2 3 4
10 11 12 13 14
Note 'inspired by "Machine Learning for .NET" by Seth Juarez'
Equivalent to the portion of Matrix.cs that begins:
public Matrix this[Func<Vector, bool> f, VectorType t]
http://machine.codeplex.com/SourceControl/changeset/view/094e8d33f44f#ml/Math/Matrix.cs
see also article by Seth Juarez in Jan 2012 issue http://www.mashedcodemagazine.com/
)
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