python numpy array 与matrix 乘方

python numpy array 与matrix 乘方

编程语言 waitig 1年前 (2017-04-18) 1272℃ 百度已收录 0评论

数组array 的乘方（**为乘方运算符）是每个元素的乘方，而矩阵matrix的乘方遵循矩阵相乘，因此必须是方阵。

2*3的数组与矩阵

>>> from numpy import * >>> import operator >>> a = array([[1,2,3],[4,5,6]]) >>> a array([[1, 2, 3], [4, 5, 6]]) >>> m = mat(a) >>> m matrix([[1, 2, 3], [4, 5, 6]]) >>> a ** 2 array([[ 1, 4, 9], [16, 25, 36]]) >>> m ** 2 Traceback (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()函数把array转化为matrix）

3*3的数组与矩阵

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