numpy.roll
- numpy. roll ( a, shift, axis=None ) [source]
-
Roll array elements along a given axis.
Elements that roll beyond the last position are re-introduced at the first.
- Parameters
-
- a array_like
-
Input array.
- shift int or tuple of ints
-
The number of places by which elements are shifted. If a tuple, then
axis
must be a tuple of the same size, and each of the given axes is shifted by the corresponding number. If an int whileaxis
is a tuple of ints, then the same value is used for all given axes. - axis int or tuple of ints, optional
-
Axis or axes along which elements are shifted. By default, the array is flattened before shifting, after which the original shape is restored.
- Returns
-
- res ndarray
-
Output array, with the same shape as
a
.
See also
-
rollaxis
-
Roll the specified axis backwards, until it lies in a given position.
Notes
New in version 1.12.0.
Supports rolling over multiple dimensions simultaneously.
Examples
>>> x = np.arange(10) >>> np.roll(x, 2) array([8, 9, 0, 1, 2, 3, 4, 5, 6, 7]) >>> np.roll(x, -2) array([2, 3, 4, 5, 6, 7, 8, 9, 0, 1])
>>> x2 = np.reshape(x, (2, 5)) >>> x2 array([[0, 1, 2, 3, 4], [5, 6, 7, 8, 9]]) >>> np.roll(x2, 1) array([[9, 0, 1, 2, 3], [4, 5, 6, 7, 8]]) >>> np.roll(x2, -1) array([[1, 2, 3, 4, 5], [6, 7, 8, 9, 0]]) >>> np.roll(x2, 1, axis=0) array([[5, 6, 7, 8, 9], [0, 1, 2, 3, 4]]) >>> np.roll(x2, -1, axis=0) array([[5, 6, 7, 8, 9], [0, 1, 2, 3, 4]]) >>> np.roll(x2, 1, axis=1) array([[4, 0, 1, 2, 3], [9, 5, 6, 7, 8]]) >>> np.roll(x2, -1, axis=1) array([[1, 2, 3, 4, 0], [6, 7, 8, 9, 5]]) >>> np.roll(x2, (1, 1), axis=(1, 0)) array([[9, 5, 6, 7, 8], [4, 0, 1, 2, 3]]) >>> np.roll(x2, (2, 1), axis=(1, 0)) array([[8, 9, 5, 6, 7], [3, 4, 0, 1, 2]])
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https://numpy.org/doc/1.22/reference/generated/numpy.roll.html