R Array


Array is R data type which has multiple dimensions. array() function creates or tests for arrays. dim() function defines the dimension of an array.

array(data=NA, dim=length(data), dimnames=NULL)

data: vector to fill the array
dim: row and col numbers
:
...

> x <- array(1:9)
> x
[1] 1 2 3 4 5 6 7 8 9

> x <- array(1:9,c(3,3))
> x
     [,1] [,2] [,3]
[1,]    1    4    7
[2,]    2    5    8
[3,]    3    6    9

> x <- 1:64
> dim(x) <- c(2,4,8) #dim() converts the vector into array
> is.array(x)
[1] TRUE

> x
, , 1

     [,1] [,2] [,3] [,4]
[1,]    1    3    5    7
[2,]    2    4    6    8

, , 2

     [,1] [,2] [,3] [,4]
[1,]    9   11   13   15
[2,]   10   12   14   16

, , 3

     [,1] [,2] [,3] [,4]
[1,]   17   19   21   23
[2,]   18   20   22   24

, , 4

     [,1] [,2] [,3] [,4]
[1,]   25   27   29   31
[2,]   26   28   30   32

, , 5

     [,1] [,2] [,3] [,4]
[1,]   33   35   37   39
[2,]   34   36   38   40

, , 6

     [,1] [,2] [,3] [,4]
[1,]   41   43   45   47
[2,]   42   44   46   48

, , 7

     [,1] [,2] [,3] [,4]
[1,]   49   51   53   55
[2,]   50   52   54   56

, , 8

     [,1] [,2] [,3] [,4]
[1,]   57   59   61   63
[2,]   58   60   62   64

> x[1,,]
     [,1] [,2] [,3] [,4] [,5] [,6] [,7] [,8]
[1,]    1    9   17   25   33   41   49   57
[2,]    3   11   19   27   35   43   51   59
[3,]    5   13   21   29   37   45   53   61
[4,]    7   15   23   31   39   47   55   63

> x[1,2,]
[1]  3 11 19 27 35 43 51 59

> x[1,2,1]
[1] 3