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Slicing A Multidimensional Array Without A For Loop
I have a 3D array r (1000 x 10 x 2000)
constructed as follows:
q = np.random.normal(size=(10,2000))
r = np.random.normal(loc=q, size=(1000,10,2000))
This array, r
, can be viewed as a 1000 x 10
matrix repeated 2000 times.
I would like to reduce this array according to the following rule:
- from each matrix select only the column which has the max value in the first row
The columns to be selected ca be obtained via: np.argmax(r[0], axis=0)
.
The result should be a 1000 x 2000
matrix.
I wonder if it is possible to get something like that without using a for
loop or list comprehensions.
Here is a for
loop which achieves the above task:
x = []
for i, idx in enumerate(np.argmax(r[0], axis=0)):
x.append(r[:,idx,i])
x = np.array(x).T
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Answer
The solution I figured looks like this:
r[:, np.argmax(r[0],axis=0), np.arange(2000)]
More elegant solutions are, of course, welcome.
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source: stackoverflow.com
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