R group columns of return trips data

Question

I have data of train trips and the number of delayed or cancelled trains that I would like to make the sum.

Start     End        Delayed Cancelled
Paris     Rome       1       0
Brussels  Berlin     4       6
Berlin    Brussels   6       2
Rome      Paris      2       1

How can I group the Start and End columns to make the sum of Paris-Rome and Rome-Paris and Brussels-Berlin and Berlin Brussels to make the total of delayed and cancelled trips by train line ?

Answer 1

Order alphabetically and summarise by group:

df |> 
  group_by(route = if_else(Start < End, paste(Start, End, sep = "-"), paste(End, Start, sep = "-"))) |> 
  summarise(Delayed = sum(Delayed), Cancelled = sum(Cancelled))

#   route           Delayed Cancelled
#   <chr>             <int>     <int>
# 1 Berlin-Brussels      10         8
# 2 Paris-Rome            3         1

Reproducible data:

df = data.frame(
  Start     = c("Paris", "Brussels", "Berlin", "Rome"),
  End       = c("Rome", "Berlin", "Brussels", "Paris"),
  Delayed   = c(1L, 4L, 6L, 2L),
  Cancelled = c(0L, 6L, 2L, 1L)
)