Using gtools::mixedsort or alternatives with dplyr::arrange

Question

I am trying to order a dataframe by making use of dplyr::arrange. The issue is that the column I am trying to sort on contains both a fixed string followed by a number, as for instance generated by the dummycode below.

  dummydf<-data.frame(values=rnorm(100),sortcol=paste0("ABC",sample(1:100,100,replace=FALSE)))

By default, using dummydf %>% arrange(sortcol) would generate a df which is sorted alphanumerically (?) but this is of course not the desired result:

values sortcol
0.708081720    ABC1
0.041348322   ABC10
1.730962886  ABC100
0.423480861   ABC11
-1.545837266   ABC12
-1.345539947   ABC13
-0.078998792   ABC14
0.088712174   ABC15
0.670583024   ABC16
1.238837680   ABC17
-1.459044293   ABC18
-2.028535223   ABC19
0.779514385    ABC2
1.360509910   ABC20

In this example, I would like to sort the column as gtools::mixedsort would do, making sure ABC2 follows ABC1 and is not preceed by ABC1-19 and ABC100 mixedsort(as.character(dummydf$sortcol)) would do that trick.

Now, I am aware I could do this by using sub in my arrange argument: dummydf %>% arrange(as.numeric(sub("ABC","",sortcol))) but that is mainly because my string is something fixed (although any regex could be used to capture the last digits following any string I suppose).

I am just wondering: is there a more "elegant" and generic way to get this done with dplyr::arrange, in the same fashion as gtools::mixedsort?

Kind regards,

FM

Answer 1

Here's a functional solution making use of the mysterious identity order(order(x)) == rank(x).

mixedrank = function(x) order(gtools::mixedorder(x))
dummydf %>% dplyr::arrange(mixedrank(sortcol))