numpy.rollaxis() in Python

numpy.rollaxis() in Python

The numpy.rollaxis() function rolls the given axis backwards until it lies in the specified position.

Syntax

numpy.rollaxis(a, axis, start=0)

Parameter

The numpy. rollaxis() method consists of three parameters, which are as follows:

a : It represents an input array.

axis : The parameter axis is used to roll backwards. The positions of the other axes do not change relative to one another.

start : It is an optional integer parameter. The axis is rolled until it lies before the start position. The default value is 0, which signifies a “complete” roll.

Return

This function returns a view of parameter ‘a’. 

Example 1

# Python Program explaining
# numpy.rollaxis() function
import numpy as np
arr = np.arange(8).reshape(2,2,2)
print ('The original array:')
print (arr)
# to roll from axis-2 to axis-0
print ('Applying rollaxis() function:')
print (np.rollaxis(arr,2)  )
# to roll from axis 0 to 1 (along width to height)
print('Applying rollaxis() function:' )
print (np.rollaxis(arr,2,1))

Output

The original array:
[[[0 1]
  [2 3]]
[[4 5]
  [6 7]]]
Applying rollaxis() function:
[[[0 2]
  [4 6]]
[[1 3]
  [5 7]]]
Applying rollaxis() function:
[[[0 2]
  [1 3]]
[[4 6]
  [5 7]]]