CODEWITHSUNDEEP
pythonnumpyscipy
Jadiel de Armas
Jadiel de Armas

Reputation: 8792

Which one is which between column slicing and row slicing?

Scipy has different kind of matrices. Two of them are the column sparse matrix and the row sparse matrix. The column sparse matrix supports fast column slicing operations and the row sparse matrix supports fast row slicing operations.

But I am not if the operation a[i,:] is a column or a row slicing operation. Any help?

Upvotes: 3

Views: 1737

Answers (1)

Davidmh
Davidmh

Reputation: 3865

There is nothing like trying it by yourself:

In [1]: import numpy as np

In [2]: np.arange(9).reshape(3,3)
Out[2]: 
array([[0, 1, 2],
       [3, 4, 5],
       [6, 7, 8]])

In [3]: a = np.arange(9).reshape(3,3)

In [4]: a[0, :]
Out[4]: array([0, 1, 2])

In [5]: a[:, 0]
Out[5]: array([0, 3, 6])

Ergo, the first index corresponds to the row and the second to the column. a[i, :] is selecting the row i, so it is a row slicing operation.

Upvotes: 4

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