Sorting rows alphabetically

Question

My data looks like,

A    B    C    D
B    C    A    D
X    Y    M    Z
O    M    L    P

How can I sort the rows to get something like

A    B    C    D
A    B    C    D
M    X    Y    Z
L    M    O    P

Thanks,

score 25 · Answer 1 · answered May 19 '11 at 19:53

25

t(apply(DF, 1, sort))

The t() function is necessary because row operations with the apply family of functions returns the results in column-major order.

answered May 19 '11 at 19:53

IRTFM

2

+1 for compact solution, plus explaining why t() is necessary – Ben Bolker May 19 '11 at 20:14
Except the explanation isn't quite right - it's not column major order, it's that new dimensions are added on to the start, not kept in their original positions. – hadley May 19 '11 at 23:20
Maybe I am not understanding our difference. `apply()` is building a matrix one column at a time, right? – IRTFM May 20 '11 at 01:47

score 6 · Answer 2 · answered May 19 '11 at 19:43

6

What did you try? This is really straight-forward and easy to solve with a simple loop.

> s <- x
> for(i in 1:NROW(x)) {
+   s[i,] <- sort(s[i,])
+ }
> s
  V1 V2 V3 V4
1  A  B  C  D
2  A  B  C  D
3  M  X  Y  Z
4  L  M  O  P

answered May 19 '11 at 19:43

Joshua Ulrich

score 2 · Answer 3 · answered May 20 '11 at 08:05

2

No plyr answer yet?!

foo <- matrix(sample(LETTERS,10^2,T),10,10)

library("plyr")

aaply(foo,1,sort)

Exactly the same as DWins answer except that you don't need t()

answered May 20 '11 at 08:05

Sacha Epskamp

score 0 · Answer 4 · answered Oct 25 '19 at 14:08

0

matrix(a[order(row(a), a, method="radix")], ncol=ncol(a))

Timings can be found here

answered Oct 25 '19 at 14:08

chinsoon12

4 Answers4