有时，我们想调换数组的维度，比如：将data变量的行维度(male, female)变为第三个维度；列维度(young, middle, old)变为行维度；第三个维度(A-D)变为列维度。在R中，可使用aperm()函数来实现这个功能：

> data

, , A

young middle old

male 1 3 5

female 2 4 6

, , B

young middle old

male 7 9 11

female 8 10 12

, , C

young middle old

male 13 15 17

female 14 16 18

, , D

young middle old

male 19 21 23

female 20 22 24

> new.data <- aperm(data, c(2,3,1)) ##调换数组的维度，将data的行维度变为第三个维度；列维度变为行维度；第三个维度变为列维度

> new.data

, , male

A B C D

young 1 7 13 19

middle 3 9 15 21

old 5 11 17 23

, , female

A B C D

young 2 8 14 20

middle 4 10 16 22

old 6 12 18 24