元素相乘:multply()
矩阵相乘:dot()、matmul()、’@’
’ * ': 是特别的。在数组操作中,作为元素相乘;在矩阵操作中作为矩阵相乘。
以下举例说明:
import numpy as np
>>> a1 = np.array([[1,2,3],[4,5,6]])
>>> b1 = np.array([1,2,3])
>>> a2 = np.array([1,2,3])
>>> b2 = np.array([1,2,3])
>>> a1 * b1 # 对应元素相乘
[[ 1 4 9]
[ 4 10 18]]
>>> a1 @ b1 # 矩阵相乘
[14 32]
>>> a2 * b2 # 对应元素相乘
[1 4 9]
>>> a2 @ b2 # 矩阵相乘
14
>>> np.multiply(a1, b1), np.multiply(a2, b2) # 对应元素相乘
(array([[ 1, 4, 9],
[ 4, 10, 18]]), array([1, 4, 9]))
>>> np.dot(a1, b1), np.dot(a2, b2) # 矩阵相乘
(array([14, 32]), 14)
>>> np.matmul(a1, b1), np.matmul(a2, b2) # 矩阵相乘
(array([14, 32]), 14)
>>> a3 = np.matrix([[1,2,3],[4,5,6]])
>>> b3_1 = np.matrix([1,2,3])
>>> b3 = np.matrix([[1],[2],[3]])
>>> a3 * b3 # 矩阵相乘
[[14]
[32]]
>>> a3 @ b3 # 矩阵相乘
[[14]
[32]]
>>> np.multiply(a3,b3_1) # 对应元素相乘
matrix([[ 1, 4, 9],
[ 4, 10, 18]])
>>> np.dot(a3, b3) # 矩阵相乘
matrix([[14],
[32]])
>>> np.matmul(a3, b3) # 矩阵相乘
matrix([[14],
[32]])