NumPy

numpy.rollaxis

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

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

This function continues to be supported for backward compatibility, but you should prefer moveaxis. The moveaxis function was added in NumPy 1.11.

Parameters
andarray

Input array.

axisint

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

startint, optional

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

Returns
resndarray

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)

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