NumPy函数库基础

矩阵

>>> from numpy import *
#求4*4随机矩阵
>>> randMat = mat(random.rand(4,4))
#求矩阵的逆矩阵
>>> invRandMat = randMat.I
>>> print randMat
[[ 0.78412287  0.54585614  0.98144309  0.31585072]
 [ 0.97836977  0.16112737  0.76317208  0.18055881]
 [ 0.08531485  0.7694393   0.41585813  0.41057737]
 [ 0.71374702  0.0135997   0.38255303  0.86235734]]
>>> print invRandMat
[[-4.2437784   4.5183152   2.07112621 -0.37777692]
 [-3.22191713  2.9476215   2.98323956 -0.85744598]
 [ 5.89650176 -4.70212925 -3.20462974  0.35060289]
 [ 0.947492   -1.70023136 -0.33963938  1.33027681]]
>>> rev = randMat * invRandMat
#计算机处理误差计算，eye(4)是创建4*4单位矩阵
>>> rev - eye(4)
matrix([[  2.22044605e-16,   1.11022302e-16,   6.80011603e-16,
           0.00000000e+00],
        [  2.22044605e-16,  -4.44089210e-16,   1.17961196e-16,
          -2.77555756e-17],
        [ -3.88578059e-16,   0.00000000e+00,  -4.44089210e-16,
           1.11022302e-16],
        [  5.55111512e-16,  -4.44089210e-16,   2.22044605e-16,
           0.00000000e+00]])