矩阵-矩阵计算

R 数据科学的线性代数

Eric Eager

Data Scientist at Pro Football Focus

矩阵乘法的动机

A%*%B

     [,1] [,2]
[1,]    2    5
[2,]    1    4

B%*%A

     [,1] [,2]
[1,]    2    1
[2,]    5    4

A*B

     [,1] [,2]
[1,]    0    2
[2,]    2    2

print(A)

     [,1] [,2]
[1,]    1    2
[2,]    2    1

I <- diag(2)
print(I)

     [,1] [,2]
[1,]    1    0
[2,]    0    1

I%*%A

     [,1] [,2]
[1,]    1    2
[2,]    2    1

A%*%I

     [,1] [,2]
[1,]    1    2
[2,]    2    1

R 数据科学的线性代数