载入数据和保存数据

In [34]: arr = np.loadtxt("/home/hadoop/wujiadong/np.txt")In [35]: np.save("/home/hadoop/wujiadong/np_out.txt",arr)

数学运算

nump.dot：矩阵乘法运算numpy.transponse：矩阵转置

求解方程组

In [39]: a = np.array([[3,6,-5],[1,-3,2],[5,-1,4]])In [40]: b = np.array([12,-2,10])In [41]: x = np.linalg.inv(a).dot(b)In [42]: xOut[42]: array([ 1.75,  1.75,  0.75])In [43]: aOut[43]: array([[ 3,  6, -5],       [ 1, -3,  2],       [ 5, -1,  4]])       In [44]: bOut[44]: array([12, -2, 10])

In [61]: d1 = np.array([[1,2,3,4],[5,6,7,8]])In [62]: d1Out[62]: array([[1, 2, 3, 4],       [5, 6, 7, 8]])In [63]: d2 = np.random.random((4,2))In [64]: d2Out[64]: array([[ 0.33936881,  0.02394269],       [ 0.55151109,  0.70094196],       [ 0.04284826,  0.80405587],       [ 0.59282838,  0.94140771]])In [65]: d1.dot(d2)Out[65]: array([[  3.94224929,   7.60362506],       [ 10.04847544,  17.48501797]])In [66]: d2.TOut[66]: array([[ 0.33936881,  0.55151109,  0.04284826,  0.59282838],       [ 0.02394269,  0.70094196,  0.80405587,  0.94140771]])In [68]: np.linalg.inv(d2.T.dot(d2))Out[68]: array([[ 3.43382891, -1.67438636],       [-1.67438636,  1.31036906]])              ##对矩阵d2进行奇异值分解 :d2=u*s*hIn [70]: u,s,h = np.linalg.svd(d2)In [71]: uOut[71]: array([[-0.11515737,  0.59645451,  0.74476033, -0.27624781],       [-0.54915702,  0.30352265, -0.53710331, -0.5637558 ],       [-0.45256189, -0.73026033,  0.3934938 , -0.32721586],       [-0.69307509,  0.13724381,  0.04488564,  0.70625514]])In [72]: sOut[72]: array([ 1.60238234,  0.47920264])In [73]: hOut[73]: array([[-0.48191562, -0.87621763],       [ 0.87621763, -0.48191562]])