numpy.rollaxis¶

numpy.rollaxis(a, axis, start=0)[source]¶

Roll the specified axis backwards, until it lies in a given position.

Parameters:

Parameters:	a : ndarray Input array. axis : int The axis to roll backwards. The positions of the other axes do not change relative to one another. start : int, optional The axis is rolled until it lies before this position. The default, 0, results in a “complete” roll.
Returns:	res : ndarray For NumPy >= 1.10.0 a view of a is always returned. For earlier NumPy versions a view of a is returned only if the order of the axes is changed, otherwise the input array is returned.

a : ndarray

Input array.

axis : int

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

start : int, optional

The axis is rolled until it lies before this position. The default, 0, results in a “complete” roll.

Returns:

res : ndarray

For NumPy >= 1.10.0 a view of a is always returned. For earlier NumPy versions a view of a is returned only if the order of the axes is changed, otherwise the input array is returned.

See also

moveaxis: Move array axes to new positions.
roll: Roll the elements of an array by a number of positions along a given axis.

Examples

>>> a = np.ones((3,4,5,6))
>>> np.rollaxis(a, 3, 1).shape
(3, 6, 4, 5)
>>> np.rollaxis(a, 2).shape
(5, 3, 4, 6)
>>> np.rollaxis(a, 1, 4).shape
(3, 5, 6, 4)