魔法陣

magic <- c(10, 24, 8, 23, 7, 12, 9, 11, 22, 26, 1, 15, 3, 14, 25, 
    13, 27, 2, 6, 17, 19, 16, 21, 5, 20, 4, 18)
dim(magic) <- c(3, 3, 3)
magic

## , , 1
## 
##      [,1] [,2] [,3]
## [1,]   10   23    9
## [2,]   24    7   11
## [3,]    8   12   22
## 
## , , 2
## 
##      [,1] [,2] [,3]
## [1,]   26    3   13
## [2,]    1   14   27
## [3,]   15   25    2
## 
## , , 3
## 
##      [,1] [,2] [,3]
## [1,]    6   16   20
## [2,]   17   21    4
## [3,]   19    5   18
## 

apply(magic, c(1, 2), sum)

##      [,1] [,2] [,3]
## [1,]   42   42   42
## [2,]   42   42   42
## [3,]   42   42   42

apply(magic, c(1, 3), sum)

##      [,1] [,2] [,3]
## [1,]   42   42   42
## [2,]   42   42   42
## [3,]   42   42   42

apply(magic, c(2, 3), sum)

##      [,1] [,2] [,3]
## [1,]   42   42   42
## [2,]   42   42   42
## [3,]   42   42   42