python numpy array 與matrix 乘方

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python numpy array 與matrix 乘方 程式設計語言 waitig 1年前 (2017-04-18) 1272℃ 百度已收錄 0評論

數組array 的乘方（**為乘方運算子）是每個元素的乘方，而矩陣matrix的乘方遵循矩陣相乘，因此必須是方陣。

2*3的數組與矩陣

>>> from numpy import *>>> import operator>>> a = array([[1,2,3],[4,5,6]])>>> aarray([[1, 2, 3],       [4, 5, 6]])>>> m = mat(a)>>> mmatrix([[1, 2, 3],        [4, 5, 6]])>>> a ** 2array([[ 1,  4,  9],       [16, 25, 36]])>>> m ** 2Traceback (most recent call last):  File "<stdin>", line 1, in <module>  File "D:\anaconda\lib\site-packages\numpy\matrixlib\defmatrix.py", line 356, in __pow__    return matrix_power(self, other)  File "D:\anaconda\lib\site-packages\numpy\matrixlib\defmatrix.py", line 173, in matrix_power    raise ValueError("input must be a square array")ValueError: input must be a square array>>> 

（mat()函數把array轉化為matrix）

3*3的數組與矩陣

>>> A = array([[1,2,3],[4,5,6],[7,8,9]])>>> Aarray([[1, 2, 3],       [4, 5, 6],       [7, 8, 9]])>>> M = mat(A)>>> Mmatrix([[1, 2, 3],        [4, 5, 6],        [7, 8, 9]])>>> A ** 2array([[ 1,  4,  9],       [16, 25, 36],       [49, 64, 81]])>>> M ** 2matrix([[ 30,  36,  42],        [ 66,  81,  96],        [102, 126, 150]])

python numpy array 與matrix 乘方