Numpy的基本操作(五)

    科技2022-07-17  112

    Numpy的基本操作(五)

    励志语录exp()sqrt()ravel()T矩阵的拼接矩阵的拆分

    励志语录

    实现自己既定的目标,必须能耐得住寂寞单干。

    exp()

    用途:实现矩阵的e的次幂操作

    代码示例:

    import numpy as np v = [1,2,3] print(np.exp(v))

    运行结果:

    [ 2.71828183 7.3890561 20.08553692]

    sqrt()

    用途:实现矩阵的次方操作

    代码示例:

    import numpy as np v = [1,2,3] print(np.sqrt(v))

    运行结果:

    [1. 1.41421356 1.73205081]

    ravel()

    用途:将矩阵拉伸成一个向量

    代码示例:

    import numpy as np m = np.array([[1,2],[3,4]]) v = m.ravel() print(v)

    运行结果:

    [1 2 3 4]

    T

    矩阵的转置

    代码示例:

    import numpy as np m = np.array([[1,2],[3,4],[5,6]]) print(m.T)

    运行结果:

    [[1 3 5] [2 4 6]]

    矩阵的拼接

    横向拼接

    函数:hstack()

    代码示例:

    import numpy as np a = np.array([[1,2,3],[1,2,3]]) b = np.array([[4,5,6],[4,5,6]]) print(np.hstack((a,b)))

    运行结果:

    [[1 2 3 4 5 6] [1 2 3 4 5 6]]

    纵向拼接

    函数:vstack()

    代码示例:

    import numpy as np a = np.array([[1,2,3],[1,2,3]]) b = np.array([[4,5,6],[4,5,6]]) print(np.vstack((a,b)))

    运行结果:

    [[1 2 3] [1 2 3] [4 5 6] [4 5 6]]

    矩阵的拆分

    横向拆分

    函数:hsplit()

    方式一:按拆分次数平均拆分

    代码示例:

    import numpy as np m = np.array([[1,2,3,4,5,6,7,8,9],[1,2,3,4,5,6,7,8,9]]) print(np.hsplit(m,3))

    运行结果:

    [array([[1, 2, 3], [1, 2, 3]]), array([[4, 5, 6], [4, 5, 6]]), array([[7, 8, 9], [7, 8, 9]])]

    方式二:给出拆分点进行拆分(拆分点以元组的方式给出)

    代码示例:

    import numpy as np m = np.array([[1,2,3,4,5,6,7,8,9],[1,2,3,4,5,6,7,8,9]]) print(np.hsplit(m,(4,5)))

    运行结果:

    [array([[1, 2, 3, 4], [1, 2, 3, 4]]), array([[5], [5]]), array([[6, 7, 8, 9], [6, 7, 8, 9]])]

    纵向拆分

    函数:vsplit()

    方式同横向拆分

    代码示例:

    import numpy as np m = np.array([[1,1],[2,2],[3,3],[4,4],[5,5],[6,6]]) print(np.vsplit(m,3))

    运行结果:

    [array([[1, 1], [2, 2]]), array([[3, 3], [4, 4]]), array([[5, 5], [6, 6]])]

    Processed: 0.009, SQL: 8