翻转矩阵flipud和fliplr函数

最新推荐文章于 2024-11-23 19:32:51 发布

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本文介绍了 numpy 中的 flipud 函数，该函数可以翻转数组的上下方向，保留行但改变其顺序。文中提供了使用示例，并说明了此操作的时间复杂度为 O(1)。此外还对比了 flipud 与 fliplr 和 rot90 的不同。

numpy.flipud

numpy.flipud(m)[source]

    Flip array in the up/down direction.

    Flip the entries in each column in the up/down direction. Rows are preserved, but appear in a different order than before.
    Parameters:

    m : array_like

        Input array.

    Returns:

    out : array_like

        A view of m with the rows reversed. Since a view is returned, this operation is \mathcal O(1).

    See also

    fliplr
        Flip array in the left/right direction.
    rot90
        Rotate array counterclockwise.

    Notes

    Equivalent to m[::-1,...]. Does not require the array to be two-dimensional.

    Examples

    >>> A = np.diag([1.0, 2, 3])
    >>> A
    array([[ 1., 0., 0.],
           [ 0., 2., 0.],
           [ 0., 0., 3.]])
    >>> np.flipud(A)
    array([[ 0., 0., 3.],
           [ 0., 2., 0.],
           [ 1., 0., 0.]])

    >>> A = np.random.randn(2,3,5)
    >>> np.all(np.flipud(A) == A[::-1,...])
    True

    >>> np.flipud([1,2])
    array([2, 1])