Module « numpy.matlib »

Fonction rollaxis - module numpy.matlib

Signature de la fonction rollaxis

def rollaxis(a, axis, start=0) 

Description

rollaxis.__doc__

    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
    ----------
    a : ndarray
        Input array.
    axis : int
        The axis to be rolled. The positions of the other axes do not
        change relative to one another.
    start : int, optional
        When ``start <= axis``, the axis is rolled back until it lies in
        this position. When ``start > axis``, the axis is rolled until it
        lies before this position. The default, 0, results in a "complete"
        roll. The following table describes how negative values of ``start``
        are interpreted:

        .. table::
           :align: left

           +-------------------+----------------------+
           |     ``start``     | Normalized ``start`` |
           +===================+======================+
           | ``-(arr.ndim+1)`` | raise ``AxisError``  |
           +-------------------+----------------------+
           | ``-arr.ndim``     | 0                    |
           +-------------------+----------------------+
           | |vdots|           | |vdots|              |
           +-------------------+----------------------+
           | ``-1``            | ``arr.ndim-1``       |
           +-------------------+----------------------+
           | ``0``             | ``0``                |
           +-------------------+----------------------+
           | |vdots|           | |vdots|              |
           +-------------------+----------------------+
           | ``arr.ndim``      | ``arr.ndim``         |
           +-------------------+----------------------+
           | ``arr.ndim + 1``  | raise ``AxisError``  |
           +-------------------+----------------------+
           
        .. |vdots|   unicode:: U+22EE .. Vertical Ellipsis

    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)