[R] a R function for sort a data frame.

[Duncan Murdoch]

On Thu, 31 Mar 2005 22:22:32 -0500, Mario Morales
<malfonso at telecom.com.co> wrote :

>Is there a R function for sort a data frame by a variable ?
>
>I know sort a vector, but I don't know sort a data frame by a
>column. Can you help me ?
>
>the sort() function don't  work with data frame.
>

This is a FAQ, but the answer there looks a bit slim to me:

7.23 How can I sort the rows of a data frame?

To sort the rows within a data frame, with respect to the values in
one or more of the columns, simply use order(). 

Here's an example that sorts on two columns:

> df <- data.frame(x = sample(1:2, 10, replace=T), y = rnorm(10))
> df
   x           y
1  1  1.50996670
2  2 -0.95740020
3  2  2.35863397
4  1  0.79743294
5  1 -1.75136964
6  2 -2.28762091
7  1  0.29517547
8  2  0.09726887
9  2  0.74852695
10 1  0.48862415
> inds <- with(df, order(x, y))
> df[inds,]
   x           y
5  1 -1.75136964
7  1  0.29517547
10 1  0.48862415
4  1  0.79743294
1  1  1.50996670
6  2 -2.28762091
2  2 -0.95740020
8  2  0.09726887
9  2  0.74852695
3  2  2.35863397