numpy矩阵运算

In [1]:

import numpy as np

 

In [2]:

# 创建3个矩阵
a = np.arange(15).reshape(3,5)
b = np.arange(15,30).reshape(3,5)
c = np.array([9,8,7,6])

 

In [3]:

a

 

Out[3]:

array([[ 0,  1,  2,  3,  4],
       [ 5,  6,  7,  8,  9],
       [10, 11, 12, 13, 14]])

 

In [4]:

b

 

Out[4]:

array([[15, 16, 17, 18, 19],
       [20, 21, 22, 23, 24],
       [25, 26, 27, 28, 29]])

 

In [5]:

c

 

Out[5]:

array([9, 8, 7, 6])

 

In [6]:

# 加
a + b

 

Out[6]:

array([[15, 17, 19, 21, 23],
       [25, 27, 29, 31, 33],
       [35, 37, 39, 41, 43]])

 

In [7]:

# 减
a - b

 

Out[7]:

array([[-15, -15, -15, -15, -15],
       [-15, -15, -15, -15, -15],
       [-15, -15, -15, -15, -15]])

 

In [8]:

# 数乘
2 * a

 

Out[8]:

array([[ 0,  2,  4,  6,  8],
       [10, 12, 14, 16, 18],
       [20, 22, 24, 26, 28]])

 

In [11]:

# 矩阵乘法
np.dot(a,b)

 

 

---------------------------------------------------------------------------
ValueError                                Traceback (most recent call last)
Cell In[11], line 2
      1 # 矩阵乘法
----> 2 np.dot(a,b)

ValueError: shapes (3,5) and (3,5) not aligned: 5 (dim 1) != 3 (dim 0)

 

In [12]:

# 转置
a = a.T
a

 

Out[12]:

array([[ 0,  5, 10],
       [ 1,  6, 11],
       [ 2,  7, 12],
       [ 3,  8, 13],
       [ 4,  9, 14]])

 

In [13]:

np.dot(a,b)

 

Out[13]:

array([[350, 365, 380, 395, 410],
       [410, 428, 446, 464, 482],
       [470, 491, 512, 533, 554],
       [530, 554, 578, 602, 626],
       [590, 617, 644, 671, 698]])

 

In [ ]: