Re: [R] multicolumn sort on dataframe?

[Spencer Graves]

     "?order" includes the following: 

   order(..., na.last = TRUE, decreasing = FALSE)

   Arguments:     ...: a sequence of vectors, all of the same length.

   Examples:

    (ii <- order(x <- c(1,1,3:1,1:4,3), y <- c(9,9:1), z <-c(2,1:9)))
    ## 6  5  2  1  7  4 10  8  3  9
    rbind(x,y,z)[,ii] # shows the reordering (ties via 2nd & 3rd arg)
 [,1] [,2] [,3] [,4] [,5] [,6] [,7] [,8] [,9] [,10]
x    1    1    1    1    2    2    3    3    3     4
y    5    6    9    9    4    7    1    3    8     2
z    5    4    1    2    6    3    9    7    2     8
     hope this helps.  spencer graves

Anne York wrote:

On Fri 26 Mar 2004, Jeff D. Hamann wrote:
                                                                               
 

I couldn't find any reference to this in the FAQ, but is it 
possible to sort a  dataframe by multiple columns?
   

                                                                               
 

I've created some code, similar to the following:
   

                                                                               
 

nspr.code <- sp.results$sp.code[order( sp.results$sp.code )]
nspr.tpa <- sp.results$tpa[order( sp.results$sp.code )]
   

                                                                               
 

nspr.code <- as.character( levels( nspr.code ) )[nspr.code]
nspr.tpa <- as.numeric( levels( nspr.tpa ) )[nspr.tpa]
   

                                                                               
 

hope <- as.data.frame( cbind( nspr.code, as.numeric(nspr.tpa) ) )
   



A simple way to sort multiple columns is to paste them 
together and sort the resulting character vector. THat way 
you only have to do one sort. This is a very old method 
taught to me in the first computer course I ever took (date 
censored); the instructor attributed the method to Von 
Neumann but I have no reference. 

You have to be careful choosing the sep character in paste. 

Here is an example

 

set.seed(78) 
foo = data.frame(x= sample(letters[1:3],5,replace=TRUE),
   

                  y= sample(1:5,5,replace=TRUE))
 

foo
   

 x y
1 c 3
2 c 2
3 b 2
4 c 1
5 c 3
Sorting on y and then by x: 

 

my.order=order(foo.paste=paste(foo[,2],foo[,1],sep="/"))
my.order
   

[1] 4 3 2 1 5

 

my.order=order(paste(foo[,1],foo[,2],sep="/"))
foo[my.order,]
   

 x y
3 b 2
4 c 1
2 c 2
1 c 3
5 c 3
 

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