array与matrix环境下的multiply、dot、*操作

numpy中数组array与矩阵matrix的乘法运算的不同，主要操作为multiply、dot、*三种。

from numpy import *

# array环境下
a =[[5,6],[7,8]]
b =[[1,2],[3,4]]
a = array(a)
b = array(b)
c = multiply(a,b)
d = dot(a,b)
e = a*b
print('a = ',a)
print('b = ',b)
print('c = multiply(a,b) = ',c)
print('d = dot(a,b)      = ',d)
print('e = a*b           = ',e)

a =  [[5 6]
 [7 8]]
b =  [[1 2]
 [3 4]]
c = multiply(a,b) =  [[ 5 12]
                      [21 32]]
d = dot(a,b)      =  [[23 34]
                      [31 46]]
e = a*b           =  [[ 5 12]
                      [21 32]]

# matrix环境下
a =[[5,6],[7,8]]
b =[[1,2],[3,4]]
a = mat(a)
b = mat(b)
c = multiply(a,b)
d = dot(a,b)
e = a*b
print('a = ',a)
print('b = ',b)
print('c = multiply(a,b) = ',c)
print('d = dot(a,b)      = ',d)
print('e = a*b           = ',e)

a =  [[5 6]
 [7 8]]
b =  [[1 2]
 [3 4]]
c = multiply(a,b) =  [[ 5 12]
                      [21 32]]
d = dot(a,b)      =  [[23 34]
                      [31 46]]
e = a*b           =  [[23 34]
                      [31 46]]

小结
数组与矩阵计算，multiply与dot运算相同。
multiply为对应位置相乘，dot为矩阵相乘。
点乘意思不同，array的点乘为对应位置相乘、matrix的点乘为矩阵乘法运算。