R语言创建矩阵

> y<-matrix(1:20,nrow = 5,ncol = 4)

> y
     [,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

> cells <- c(1,26,24,68)

> rnames <- c("R1","R2")

> cnames <- c("C1","C2")

> #按行填充
> mymatrix <- matrix(cells,nrow = 2,ncol = 2,byrow = TRUE,dimnames = list(rnames,cnames))

> mymatrix
   C1 C2
R1  1 26
R2 24 68

> #按列填充
> mymatrix <- matrix(cells,nrow = 2,ncol = 2,byrow = FALSE,dimnames = list(rnames,cnames))

> mymatrix
   C1 C2
R1  1 24
R2 26 68

> #矩阵下标使用
> 
> i <- matrix(1:10,nrow = 2)

> i
     [,1] [,2] [,3] [,4] [,5]
[1,]    1    3    5    7    9
[2,]    2    4    6    8   10

> i[2,]
[1]  2  4  6  8 10

> i[,2]
[1] 3 4

> i[1,4]
[1] 7

> i[1,c(4,5)]
[1] 7 9