R语言入门（7）-矩阵运算

> m+1
   C1 C2 C3 C4 C5
R1  2  6 10 14 18
R2  3  7 11 15 19
R3  4  8 12 16 20
R4  5  9 13 17 21

> n<-matrix
> n<-matrix(1:20,5,4)
> n
     [,1] [,2] [,3] [,4]
[1,]    1    6   11   16
[2,]    2    7   12   17
[3,]    3    8   13   18
[4,]    4    9   14   19
[5,]    5   10   15   20
> m+n
Error in m + n : non-conformable arrays

> m[1,]
C1 C2 C3 C4 C5 
 1  5  9 13 17 
> sum(m[1,])
[1] 45
> colSums(m)
C1 C2 C3 C4 C5 
10 26 42 58 74 
> rowSums(m)
R1 R2 R3 R4 
45 50 55 60 
> colMeans(m)
  C1   C2   C3   C4   C5 
 2.5  6.5 10.5 14.5 18.5 
> rowMeans(m)
R1 R2 R3 R4 
 9 10 11 12 

 注意：矩阵乘积运算中内积运算与外积运算对行与列的要求不同，内积的行列数要求完全相等，外积的矩阵1的列数等于矩阵2的行数即可。

> n<- matrix(1:12,3,4)
> m<- matrix(2:13,3,4)
> m+n
     [,1] [,2] [,3] [,4]
[1,]    3    9   15   21
[2,]    5   11   17   23
[3,]    7   13   19   25
> m*n
     [,1] [,2] [,3] [,4]
[1,]    2   20   56  110
[2,]    6   30   72  132
[3,]   12   42   90  156
> m %*% n
Error in m %*% n : non-conformable arguments
> n<- matrix(1:12,4,3)
> m*n
Error in m * n : non-conformable arrays
> m %*% n
     [,1] [,2] [,3]
[1,]   80  184  288
[2,]   90  210  330
[3,]  100  236  372

对角线数值输出、矩阵转置 

> diag(n)
[1]  1  6 11

> t(n)
     [,1] [,2] [,3] [,4]
[1,]    1    2    3    4
[2,]    5    6    7    8
[3,]    9   10   11   12