Dail - 1 year ago 101

R Question

I have a simple matrix like:

`> a = matrix(c(c(1:10),c(10:1)), ncol=2)`

> a

[,1] [,2]

[1,] 1 10

[2,] 2 9

[3,] 3 8

[4,] 4 7

[5,] 5 6

[6,] 6 5

[7,] 7 4

[8,] 8 3

[9,] 9 2

[10,] 10 1

I would like to get this result:

`[,1] [,2]`

[1,] 10 1

[2,] 9 2

[3,] 8 3

[4,] 7 4

[5,] 6 5

[6,] 5 6

[7,] 4 7

[8,] 3 8

[9,] 2 9

[10,] 1 10

The exact reverse of the matrix. How can I get it?

Thanks

Answer Source

Try `rev`

with `apply`

:

```
> a <- matrix(c(1:10,10:1), ncol=2)
> a
[,1] [,2]
[1,] 1 10
[2,] 2 9
[3,] 3 8
[4,] 4 7
[5,] 5 6
[6,] 6 5
[7,] 7 4
[8,] 8 3
[9,] 9 2
[10,] 10 1
> b <- apply(a, 2, rev)
> b
[,1] [,2]
[1,] 10 1
[2,] 9 2
[3,] 8 3
[4,] 7 4
[5,] 6 5
[6,] 5 6
[7,] 4 7
[8,] 3 8
[9,] 2 9
[10,] 1 10
```