Question

我在R中有一个像这样的矩阵：

|1|2|3|
|1|2|3|
|1|2|3|

是否有一种简单的方法可以将整个矩阵顺时针旋转90度以获得这些结果？

|1|1|1|
|2|2|2|
|3|3|3|

再次旋转90度：

|3|2|1|
|3|2|1|
|3|2|1|

Answer 1

t不会旋转条目，它会沿着对角线翻转：

x <- matrix(1:9, 3)
x
##      [,1] [,2] [,3]
## [1,]    1    4    7
## [2,]    2    5    8
## [3,]    3    6    9

t(x)
##      [,1] [,2] [,3]
## [1,]    1    2    3
## [2,]    4    5    6
## [3,]    7    8    9

R矩阵顺时针旋转90度：

您还需要在转置之前反转列：

rotate <- function(x) t(apply(x, 2, rev))
rotate(x)
##      [,1] [,2] [,3]
## [1,]    3    2    1
## [2,]    6    5    4
## [3,]    9    8    7

rotate(rotate(x))
##      [,1] [,2] [,3]
## [1,]    9    6    3
## [2,]    8    5    2
## [3,]    7    4    1

rotate(rotate(rotate(x)))
##      [,1] [,2] [,3]
## [1,]    7    8    9
## [2,]    4    5    6
## [3,]    1    2    3

rotate(rotate(rotate(rotate(x))))
##      [,1] [,2] [,3]
## [1,]    1    4    7
## [2,]    2    5    8
## [3,]    3    6    9

R矩阵逆时针旋转90度：

在反向之前进行转置与逆时针旋转相同：

foo = matrix(1:9, 3)
foo
## [,1] [,2] [,3]
## [1,]    1    4    7
## [2,]    2    5    8
## [3,]    3    6    9

foo <- apply(t(foo),2,rev)
foo

## [,1] [,2] [,3]
## [1,]    7    8    9
## [2,]    4    5    6
## [3,]    1    2    3

Answer 2

m <- matrix(rep(1:3,each=3),3)

     [,1] [,2] [,3]
[1,]    1    2    3
[2,]    1    2    3
[3,]    1    2    3

t(m[nrow(m):1,])

     [,1] [,2] [,3]
[1,]    1    1    1
[2,]    2    2    2
[3,]    3    3    3

m[nrow(m):1,ncol(m):1]

     [,1] [,2] [,3]
[1,]    3    2    1
[2,]    3    2    1
[3,]    3    2    1

t(m)[ncol(m):1,]

     [,1] [,2] [,3]
[1,]    3    3    3
[2,]    2    2    2
[3,]    1    1    1

Answer 3

将矩阵旋转 180°的简单方法是：

m <- matrix(1:8,ncol=4)
#      [,1] [,2] [,3] [,4]
# [1,]    1    3    5    7
# [2,]    2    4    6    8


rot <- function(x) "[<-"(x, , rev(x))

rot(m)
#      [,1] [,2] [,3] [,4]
# [1,]    8    6    4    2
# [2,]    7    5    3    1

rot(rot(m))
#      [,1] [,2] [,3] [,4]
# [1,]    1    3    5    7
# [2,]    2    4    6    8

Answer 4

将矩阵旋转90度和-90度

的R方法

#first reverse, then transpose, it's the same as rotate 90 degrees
rotate_clockwise         <- function(x) { t(     apply(x, 2, rev))}
#first transpose, then reverse, it's the same as rotate -90 degrees:
rotate_counter_clockwise <- function(x) { apply(     t(x),2, rev)}

#or if you want a library to help make things easier to read:
#install.packages("pracma")
library(pracma)
rotate_one_eighty <- function(x) { rot90(x, 2) }
rotate_two_seventy <- function(x) { rot90(x, -1) }

foo = matrix(1:9, 3)
foo

foo = rotate_clockwise(foo)
foo

foo = rotate_counter_clockwise(foo)
foo

foo = rotate_one_eighty(foo)
foo

打印：

     [,1] [,2] [,3]
[1,]    1    4    7          #original matrix
[2,]    2    5    8
[3,]    3    6    9
     [,1] [,2] [,3]
[1,]    3    2    1
[2,]    6    5    4          #rotated 90 degrees
[3,]    9    8    7
     [,1] [,2] [,3]
[1,]    1    4    7
[2,]    2    5    8          #rotated -90 degrees
[3,]    3    6    9
     [,1] [,2] [,3]
[1,]    9    6    3
[2,]    8    5    2          #rotated 180 degrees
[3,]    7    4    1

请注意，顺时针旋转矩阵，然后逆时针将数字返回到原始位置，然后旋转180就像旋转90次一样。

Answer 5

或组合在一个功能中（基于Eric Leschinski）：

rotate  <- function(x, clockwise=T) {
  if (clockwise) { t( apply(x, 2, rev))
  } else {apply( t(x),2, rev)} 
}

在R中旋转矩阵

5 个答案:

将矩阵旋转90度和-90度