機器學習篇:Python,NumPy函式庫基礎
阿新 • • 發佈:2018-12-14
NumPy函式庫基礎 (參考自《機器學習實戰》)
先開啟Pyhton
>>> from numpy import * 引入NumPy函式庫所有模組
>>> random.rand(4,4) 隨機建立4x4矩陣
>>> randMat=mat(random.rand(4,4)) 賦值語句
>>> randMat.I 矩陣求逆
>>> invRandMat=randMat.I 賦值語句
>>> randMat*invRandMat 矩陣相乘(矩陣乘以它的逆矩陣結果應當是單位矩陣(除了對角線元素是1,4x4矩陣其他元素應該全是0)
>>> myEye=randMat*invRandMat 賦值語句
>>> myEye-eye(4) eye(4)的作用是建立一個4x4大小的單位矩陣
下面是執行結果,另一方面,如果這些函式都能正常執行,說明已經正確安裝NumPy函式庫,否則,請移步
>>> 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下面測試,只需要把需要顯示的物件使用print函式打印出來