矩阵定义

定义常规矩阵

import numpy as np
from numpy import *

x=array([[1,1,1],[2,2,2]])

print("X:",X2)
print("X[0]:",X2[0])

定义0矩阵

import numpy as np
from numpy import *

a=zeros(3)
b=zeros((4,3))

#矩阵切片
c=b[1:3,2:4]
print("a:",a)
print("b:",b)
print("c:",c)

矩阵调用

转置

x=array([[1,1,1],[2,2,2]])
y=x.T #转置

print("y:",y)

逆

对A求逆矩阵可直接用 B=np.linalg.inv(A)，若需要判断是否可逆则见下文：

import numpy as np
from numpy import *

try:
    A = np.array([[1,1],[2,-2]])
    print(A)
    B=np.linalg.inv(A)
except:
    print("矩阵不存在逆矩阵")
else:
    print(B)

矩阵不存在见下图：

乘积

点乘

import numpy as np
from numpy import *

x=array([[1,1],[2,2],[2,2]])
x1=array([[1,1,1],[2,2,2]])
A=np.dot(x1,x)
print(A)

叉乘

直接乘号*