机器学习篇：Python，NumPy函数库基础

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Python基础：https://blog.csdn.net/qq_34374664/article/details/80012978

NumPy函数库基础 （参考自《机器学习实战》）

先打开Pyhton

>>> from numpy import * 引入NumPy函数库所有模块

>>> random.rand(4,4) 随机创建4x4矩阵

>>> randMat=mat(random.rand(4,4)) 赋值语句

>>> randMat.I 矩阵求逆

>>> invRandMat=randMat.I 赋值语句

>>> randMat*invRandMat 矩阵相乘（矩阵乘以它的逆矩阵结果应当是单位矩阵（除了对角线元素是1,4x4矩阵其他元素应该全是0））

>>> myEye=randMat*invRandMat 赋值语句

>>> myEye-eye(4) eye（4）的作用是创建一个4x4大小的单位矩阵

下面是运行结果，另一方面，如果这些函数都能正常运行，说明已经正确安装NumPy函数库，否则，请移步

https://blog.csdn.net/qq_15020543/article/details/82950509

>>> from numpy import *
>>> random.rand(4,4)
array([[0.52968867, 0.27295897, 0.43328778, 0.15351488],
       [0.38746148, 0.96991943, 0.31615279, 0.97758276],
       [0.17381753, 0.69937117, 0.36569362, 0.59213545],
       [0.63289993, 0.85300831, 0.05252367, 0.33017053]])
>>> randMat=mat(random.rand(4,4))
>>> randMat.I
matrix([[-3.67137963,  5.61616605, -5.24930488,  4.42793174],
        [ 0.7807113 , -4.00703711,  2.87491373, -1.06612482],
        [ 2.53688143, -0.62544835,  2.97554257, -3.04149837],
        [ 1.12031781, -0.34828213, -0.49333309,  0.44188235]])
>>> invRandMat=randMat.I
>>> randMat*invRandMat
matrix([[ 1.00000000e+00,  7.59160956e-17,  5.12264156e-17,
          5.29937977e-17],
        [ 8.74862671e-17,  1.00000000e+00,  1.59897727e-16,
         -1.95691465e-16],
        [-4.54604422e-16,  4.92732200e-16,  1.00000000e+00,
          1.93028444e-16],
        [-5.51365126e-16,  4.39589407e-16, -6.40992479e-16,
          1.00000000e+00]])
>>> myEye=randMat*invRandMat
>>> myEye-eye(4)
matrix([[ 0.00000000e+00,  7.59160956e-17,  5.12264156e-17,
          5.29937977e-17],
        [ 8.74862671e-17,  2.22044605e-16,  1.59897727e-16,
         -1.95691465e-16],
        [-4.54604422e-16,  4.92732200e-16, -1.11022302e-16,
          1.93028444e-16],
        [-5.51365126e-16,  4.39589407e-16, -6.40992479e-16,
          2.22044605e-16]])

如果在VS2017下面测试，只需要把需要显示的对象使用print函数打印出来