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How to shuffle columns or rows of matrix in PyTorch?
A matrix in PyTorch is a 2-dimension tensor having elements of the same dtype. We can shuffle a row by another row and a column by another column. To shuffle rows or columns, we can use simple slicing and indexing as we do in Numpy.
If we want to shuffle rows, then we do slicing in the row indices.
To shuffle columns, we do slicing in the column indices.
For example, if we want to shuffle the 1st and 2nd rows of a 3☓3 matrix, then we just shuffle the index of these rows and make a slicing to find the shuffled matrix.
Let's take a couple of examples to have a better understanding of how it works.
Steps
You could use the following steps to shuffle the rows or columns of a matrix.
Import the required library. In all the following examples, the required Python library is torch. Make sure you have already installed it.
import torch
Define a matrix and print it.
matrix = torch.tensor([[1., 2., 3.],[4., 5., 6.],[7, 8, 9]])
print("Original Matrix:
", matrix)Specify the row and column indices with shuffled indices. In the following example we shuffle 1st and 2nd row. So, we interchanged the indices of these rows.
# shuffle 1st and second row r = torch.tensor([1, 0, 2]) c = torch.tensor([0, 1, 2])
Shuffle the rows or columns of the matrix.
matrix=matrix[r[:, None], c] # shuffles rows matrix = matrix[r][:,c] # shuffles columns
Print the shuffled matrix.
print("Shuffled Matrix:
", matrix)Example 1
In the following example, we shuffle the 1st and 2nd rows.
# Import the required library
import torch
# create a matrix
matrix = torch.tensor([[1., 2., 3.],[4., 5., 6.],[7, 8, 9]])
# print matrix
print("Original Matrix:
", matrix)
# shuffle 1st and second row
r = torch.tensor([1, 0, 2])
c = torch.tensor([0, 1, 2])
matrix=matrix[r[:, None], c]
print("Shuffled Matrix:
", matrix)Output
Original Matrix: tensor([[1., 2., 3.], [4., 5., 6.], [7., 8., 9.]]) Shuffled Matrix: tensor([[4., 5., 6.], [1., 2., 3.], [7., 8., 9.]])
Notice that the 1st and 2nd rows are shuffled.
Example 2
In the following example, we shuffle 2nd and 3rd columns.
# Import the required library
import torch
# create a matrix
matrix = torch.tensor([[1., 2., 3.],[4., 5., 6.],[7, 8, 9]])
# print matrix
print("Original Matrix:
", matrix)
# shuffle 2nd and 3rd columns
r = torch.tensor([0, 1, 2])
c = torch.tensor([0, 2, 1])
matrix_col_Shuffled = matrix[r][:,c]
print("Shuffled Matrix:
", matrix_col_Shuffled)Output
Original Matrix: tensor([[1., 2., 3.], [4., 5., 6.], [7., 8., 9.]]) Shuffled Matrix: tensor([[1., 3., 2.], [4., 6., 5.], [7., 9., 8.]])
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