從numpy二維數組中乘以列向量和行向量形成一個不同的1d數組

Question

如何將每個列向量與數組中的標量相乘？

例

a b c      x1a x2b x3c 
a b c  x1 x2 x3  -> x1a x2b x3c 
a b c      x1a x2b x3c 
a b c      x1a x2b x3c 

---

如何乘以每一行向量與來自陣列的標量？

例

一個更好的主題

a a a a      x1a x1a x1a x1a 
b b b b  x1 x2 x3  -> x2b x2b x2b x2b 
c c c c      x3c x3c x3c x3c 

建議將理解

Answer 1

我更喜歡下面的語法，這是短期的，但明確

A = np.ones((3,4)) 
B = np.arange(3) 
print A * B[:,None] 

>>> array([[ 0., 0., 0., 0.], 
     [ 1., 1., 1., 1.], 
     [ 2., 2., 2., 2.]]) 

A = np.ones((4,3)) 
B = np.arange(3) 
print A * B[None,:] 
>>> array([[ 0., 1., 2.], 
     [ 0., 1., 2.], 
     [ 0., 1., 2.], 
     [ 0., 1., 2.]]) 

Answer 2

1.柱乘法

In [39]: A = array([[1,2,3],[1,2,3],[1,2,3],[1,2,3]]) 

In [40]: X = array([10,20,30]) 

In [41]: A 
Out[41]: 
array([[1, 2, 3], 
     [1, 2, 3], 
     [1, 2, 3], 
     [1, 2, 3]]) 

In [42]: X 
Out[42]: array([10, 20, 30]) 

In [43]: A * X 
Out[43]: 
array([[10, 40, 90], 
     [10, 40, 90], 
     [10, 40, 90], 
     [10, 40, 90]]) 

---

1行乘法

In [44]: B = array([[1,1,1,1],[2,2,2,2],[3,3,3,3]]) 

In [45]: B 
Out[45]: 
array([[1, 1, 1, 1], 
     [2, 2, 2, 2], 
     [3, 3, 3, 3]]) 

In [46]: X = array([10,20,30]) 

In [47]: X 
Out[47]: array([10, 20, 30]) 

In [48]: (B.transpose() * X).transpose() 
Out[48]: 
array([[10, 10, 10, 10], 
     [40, 40, 40, 40], 
     [90, 90, 90, 90]])