如何在 numpy 中获得逐元素矩阵乘法(Hadamard 乘积)? [英] How to get element-wise matrix multiplication (Hadamard product) in numpy?
问题描述
我有两个矩阵
a = np.matrix([[1,2], [3,4]])
b = np.matrix([[5,6], [7,8]])
我想得到元素乘积,[[1*5,2*6], [3*7,4*8]]
,等于
and I want to get the element-wise product, [[1*5,2*6], [3*7,4*8]]
, equaling
[[5,12], [21,32]]
我试过了
print(np.dot(a,b))
和
print(a*b)
但两者都给出结果
[[19 22], [43 50]]
这是矩阵乘积,而不是逐元素乘积.如何使用内置函数获取元素级乘积(又名 Hadamard 乘积)?
which is the matrix product, not the element-wise product. How can I get the the element-wise product (aka Hadamard product) using built-in functions?
推荐答案
对于 matrix
对象的元素乘法,您可以使用 numpy.multiply
:
For elementwise multiplication of matrix
objects, you can use numpy.multiply
:
import numpy as np
a = np.array([[1,2],[3,4]])
b = np.array([[5,6],[7,8]])
np.multiply(a,b)
结果
array([[ 5, 12],
[21, 32]])
然而,你真的应该使用 array
而不是 matrix
.matrix
对象与常规 ndarray 有各种可怕的不兼容.使用 ndarrays,您可以只使用 *
进行元素乘法:
However, you should really use array
instead of matrix
. matrix
objects have all sorts of horrible incompatibilities with regular ndarrays. With ndarrays, you can just use *
for elementwise multiplication:
a * b
如果您使用的是 Python 3.5+,您甚至不会失去使用运算符执行矩阵乘法的能力,因为 @
现在做矩阵乘法:
If you're on Python 3.5+, you don't even lose the ability to perform matrix multiplication with an operator, because @
does matrix multiplication now:
a @ b # matrix multiplication
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