Hello,
The following is an example where an array element assignment didn't work
as I expected.
Create a 6 x 3 matrix:
In [70]: a = randn(6,3)
In [71]: a
Out[71]:
array([[ 1.73266816, 0.948849 , 0.69188222],
[-0.61840161, -0.03449826, 0.15032552],
[ 0.4963306 , 0.77028209, -0.63076396],
[-1.92273602, -1.03146536, 0.27744612],
[ 0.70736325, 1.54687964, -0.75573888],
[ 0.16316043, -0.34814532, 0.3683143 ]])
Create a 3x3 boolean array:
In [72]: mask = randn(3,3)>0.
In [73]: mask
Out[73]:
array([[ True, True, True],
[False, True, True],
[ True, False, True]], dtype=bool)
Try to modify elements of "a" with the following line:
In [74]: a[(2,3,5),][mask] = 1.
No elements are changed in "a":
In [75]: a
Out[75]:
array([[ 1.73266816, 0.948849 , 0.69188222],
[-0.61840161, -0.03449826, 0.15032552],
[ 0.4963306 , 0.77028209, -0.63076396],
[-1.92273602, -1.03146536, 0.27744612],
[ 0.70736325, 1.54687964, -0.75573888],
[ 0.16316043, -0.34814532, 0.3683143 ]])
Instead try to modify elements of "a" with this line:
In [76]: a[::2,][mask] = 1.
This time it works:
In [77]: a
Out[77]:
array([[ 1. , 1. , 1. ],
[-0.61840161, -0.03449826, 0.15032552],
[ 0.4963306 , 1. , 1. ],
[-1.92273602, -1.03146536, 0.27744612],
[ 1. , 1.54687964, 1. ],
[ 0.16316043, -0.34814532, 0.3683143 ]])
Is there a way where I can modify the elements of "a" selected by an
expression like "a[(2,3,5),][mask]" ?
Thanks , Emil
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