Python 中矩阵的子集递增
我想增加矩阵的一小部分（变量）[下面的说明性代码] - 但通过循环运行它们似乎很草率且不优雅 - 我怀疑这是执行此计算的最慢方法。 我的想法之一是创建另一个由 1 组成的数组，其尺寸是我想要增加的（在下面的示例中为 2x3），并用零填充这个临时数组，使其与原始数组具有相同的尺寸。然后我可以将它们相加。
不确定如何在 numpy 中完成此填充 - 或者这是否是执行此计算的最高效方法？我想尝试尽可能地优化它。
>>> import numpy as np
>>> a = np.zeros((10,10))
>>> for i in range(3,5):
... for x in range(4,7):
... a[i][x] += 1
>>> a
array([[ 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., 1., 1., 1., 0., 0., 0.],
[ 0., 0., 0., 0., 1., 1., 1., 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.]])
I want to increment a small subsection (variable) of an matrix [illustrative code below] - but running over them by loops seems sloppy and inelegant -- and I suspect is the slowest way to do this calc.
One of the ideas I had was to create another array of ones, of the dimensions that i want to increment (2x3 in example below) and to pad this temporary array with zeros so it was of the same dimensions as the original. I could then sum them.
Not sure how to accomplish this padding in numpy - or if that is the most performant way of doing this calculation? I'd like to try and optimize this as much as possible.
>>> import numpy as np
>>> a = np.zeros((10,10))
>>> for i in range(3,5):
... for x in range(4,7):
... a[i][x] += 1
>>> a
array([[ 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., 1., 1., 1., 0., 0., 0.],
[ 0., 0., 0., 0., 1., 1., 1., 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.]])
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您可以简单地通过以下方式执行相同操作：
You can do the same simply by:
您还可以使用逻辑数组来访问子集的各个元素。当您的子集具有不规则形状时特别方便。
他们的表现也非常好。例如
You can use also logical arrays for accessing individual elements of your subset. Especially handy when your subset has irregular shape.
Also they perform very well. For example