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 while axis 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])
>>> 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, 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]])