[Numpy-discussion] Selecting columns of a matrix
Keith Goodman
kwgoodman at gmail.com
Wed Jun 21 09:56:42 CDT 2006
Alan G Isaac wrote:
> M.transpose()[V>0]
> If you want the columns as columns,
> you can transpose again.
I can't get that to work when M is a n by m matrix:
>> M = asmatrix(rand(3,4))
>> M
matrix([[ 0.78970407, 0.78681448, 0.79167808, 0.57857822],
[ 0.44567836, 0.23985597, 0.49392248, 0.0282004 ],
[ 0.7044725 , 0.4090776 , 0.12035218, 0.71365101]])
>> V = asmatrix(rand(4,1))
>> V
matrix([[ 0.61638738],
[ 0.76928157],
[ 0.3882811 ],
[ 0.68979661]])
>> M.transpose()[V > 0.5]
matrix([[ 0.78970407, 0.78681448, 0.57857822]])
The answer should be a 3 by 3 matrix.
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