I am looking for replacing zones in array, for example I create an array b = numpy.zeros((12,12)). And I want to change its values with a=numpy.aray([[1,2],[2,3]]) in the left upper corner indexed by [0:1,0:1].
When I specify b[0:1,0:1] = a I have an error:
"ValueError: output operand requires a reduction, but reduction is not enabled".
What's the method to do such thing ?
Thanks
Use correct indices:
>>> b[0:2,0:2] = a
>>> b
array([[ 1., 2., 0., 0., 0., 0., 0., 0., 0., 0., 0., 0.],
[ 2., 3., 0., 0., 0., 0., 0., 0., 0., 0., 0., 0.],
[ 0., 0., 0., 0., 0., 0., 0., 0., 0., 0., 0., 0.],
[ 0., 0., 0., 0., 0., 0., 0., 0., 0., 0., 0., 0.],
[ 0., 0., 0., 0., 0., 0., 0., 0., 0., 0., 0., 0.],
[ 0., 0., 0., 0., 0., 0., 0., 0., 0., 0., 0., 0.],
[ 0., 0., 0., 0., 0., 0., 0., 0., 0., 0., 0., 0.],
[ 0., 0., 0., 0., 0., 0., 0., 0., 0., 0., 0., 0.],
[ 0., 0., 0., 0., 0., 0., 0., 0., 0., 0., 0., 0.],
[ 0., 0., 0., 0., 0., 0., 0., 0., 0., 0., 0., 0.],
[ 0., 0., 0., 0., 0., 0., 0., 0., 0., 0., 0., 0.],
[ 0., 0., 0., 0., 0., 0., 0., 0., 0., 0., 0., 0.]])
From the docs:
One way to remember how slices work is to think of the indices as pointing between characters, with the left edge of the first character numbered 0. Then the right edge of the last character of a string of n characters has index n, for example:
+---+---+---+---+---+
| H | e | l | p | A |
+---+---+---+---+---+
0 1 2 3 4 5
-5 -4 -3 -2 -1
2 denotes the end of the second element (see the scheme at the end of my answer). So [0:2] is actually the first and the second elements of the sequence.
numpyuses the same conventions as Python for slicing. For the basics of Python slicing, see this question.