从3D numpy数组中提取2D

Question

I have two 3D arrays of the form (1000, 1000, 20). The last dimension, 13, is an index through time stamps. I want to step through the arrays by time stamps and compare arrays. Suppose I have A (1000, 1000, 20) and B(1000, 1000, 20).

I want something like

for t in range(0,21):   
     asub = A[,,t]  
     bsub = B[,,t]  
     #compare asub and bsub

However, that syntax does not seem to work. how can I do this?

Answer 1

From the documentation , you need to "Combine advanced and basic indexing" .

So advanced indexing involves indexing specific axis of an array .

For example, taking the elements from index 1 onwards:

>>> a = np.array([[1,2,3], [4,5,6],[7,8,9]])
>>> a[1:, 1:]
array([[5, 6],
       [8, 9]])

So if you want to get the element from the third axis at index t , you need to select all the elements from the other axis with just a regular colon ( : ) and then specify t for the last index :

So you want to do:

A[:, :, t]