[Numpy-discussion] addressing a submatrix
Martin Wiechert
martin.wiechert at gmx.de
Wed Jun 14 04:14:17 CDT 2006
Hi list,
is there a concise way to address a subrectangle of a 2d array? So far I'm
using
A [I] [:, J]
which is not pretty and more importantly only works for reading the
subrectangle. Writing does *not* work. (Cf. session below.)
Any help would be appreciated.
Thanks,
Martin
In [1]:a = zeros ((4,4))
In [2]:b = ones ((2,2))
In [3]:c = array ((1,2))
In [4]:a [c] [:, c] = b
In [5]:a
Out[5]:
array([[0, 0, 0, 0],
[0, 0, 0, 0],
[0, 0, 0, 0],
[0, 0, 0, 0]])
In [6]:a [:, c] [c] = b
In [7]:a
Out[7]:
array([[0, 0, 0, 0],
[0, 0, 0, 0],
[0, 0, 0, 0],
[0, 0, 0, 0]])
In [8]:a [c, c] = b
In [9]:a
Out[9]:
array([[0, 0, 0, 0],
[0, 1, 0, 0],
[0, 0, 1, 0],
[0, 0, 0, 0]])
In [10]:a [c] [:, c]
Out[10]:
array([[1, 0],
[0, 1]])
In [11]:
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