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  • Numpy

    一. Numpy 常用操作

    a. xxxx

    import numpy as np
    
    print(np.arange(1,11))
        #[ 1  2  3  4  5  6  7  8  9 10]
    
    print(np.arange(1,11).reshape([2,5]))
        #  [
        #    [ 1  2  3  4  5]
        #    [ 6  7  8  9 10]
        #  ]
    
    
    li = np.arange(1,11).reshape([2,5])
    
    print(li)
        # [
        #    [ 1  2  3  4  5]
        #    [ 6  7  8  9 10]
        # ]
    print(np.exp(li))   #自然指数
        # [
        #    [  2.71828183e+00   7.38905610e+00   2.00855369e+01   5.45981500e+01  1.48413159e+02]
        #    [  4.03428793e+02   1.09663316e+03   2.98095799e+03   8.10308393e+03  2.20264658e+04]
        # ]
    print(np.exp2(li))  #自然指数的平方
        # [
        #    [    2.     4.     8.    16.    32.]
        #    [   64.   128.   256.   512.  1024.]
        # ]
    print(np.sqrt(li))  #开方
        # [
        #   [ 1.          1.41421356  1.73205081  2.          2.23606798]
        #   [ 2.44948974  2.64575131  2.82842712  3.          3.16227766]
        # ]
    View Code

    b. 单个数组操作

    li = np.array([
        [[1,2,3,4],[4,5,6,7]],
        [[7,8,9,10],[10,11,12,13]],
        [[14,15,16,17],[18,19,20,21]]
    ])
    print(li.sum())     #求和
        #252
    print(li.sum(axis=0))   #最外层
        # [
        #    [22 25 28 31]
        #    [32 35 38 41]
        # ]
    print(li.sum(axis=1))   #第一层
        # [
        #   [ 5  7  9 11]
        #   [17 19 21 23]
        #   [32 34 36 38]
        # ]
    print(li.sum(axis=2))
        # [
        #   [10 22]
        #   [34 46]
        #   [62 78]
        # ]
    View Code

    c. 多个数组操作

    #多个数组操作
    
    li1 = np.array([10,20,30,40])
    li2 = np.array([4,3,2,1])
    
    print(li1.reshape([2,2]),li2.reshape([2,2]))
        # [ [10 20][30 40] ]
        # [ [4 3][2 1]   ]
    
    print(np.dot(li1.reshape([2,2]),li2.reshape([2,2])))
        # [ [ 80  50][200 130] ]
    
    
    print(np.concatenate((li1,li2)))       #追加
        # [10 20 30 40  4  3  2  1]
    print(np.vstack((li1,li2)))
        # [[10 20 30 40] [ 4  3  2  1]]
    print(np.hstack((li1,li2)))
        # [10 20 30 40  4  3  2  1]
    
    
    print(np.split(li1,2))                 #分开
        #[array([10, 20]), array([30, 40])]
    View Code

    二.  线性方程组 矩阵

    import numpy as np
    from numpy.linalg import *
    
    #numpy 线性方程组 和矩阵
    
    #print(np.eye(3))        #矩阵
        #[[ 1.  0.  0.]
        # [ 0.  1.  0.]
        # [ 0.  0.  1.]]
    
    li = np.array([         #自定义矩阵
        [1.,2.],[3.,4.]
    ])
    #print(li)
        # [[ 1.  2.][ 3.  4.]]
    
    print(inv(li))
        # [[-2.   1. ][ 1.5 -0.5]]
    
    print(li.transpose())
        # [[ 1.  3.][ 2.  4.]]
    
    print(det(li))
        # -2.0
    
    print(eig(li))
        #(array([-0.37228132,  5.37228132]), array([[-0.82456484, -0.41597356],[ 0.56576746, -0.90937671]]))
    View Code

     

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  • 原文地址:https://www.cnblogs.com/golangav/p/7400395.html
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