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Module « numpy.matlib »

Fonction roll - module numpy.matlib

Signature de la fonction roll

def roll(a, shift, axis=None) 

Description

help(numpy.matlib.roll)

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
-----
Supports rolling over multiple dimensions simultaneously.

Examples
--------
>>> import numpy as np
>>> 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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