Reorder the data frame using arrange

The dplyr package has a function called arrange that is used to sort/reorder data frames according to the values of the specified variable. This is often used after we have used the group_by and summarize functions as we will see.

Let's suppose we were interested in determining the most frequent destination airports from New York City in 2013:

freq_dest <- flights %>% 
  group_by(dest) %>% 
  summarize(num_flights = n())
freq_dest

# A tibble: 105 x 2
   dest  num_flights
   <chr>       <int>
 1 ABQ           254
 2 ACK           265
 3 ALB           439
 4 ANC             8
 5 ATL         17215
 6 AUS          2439
 7 AVL           275
 8 BDL           443
 9 BGR           375
10 BHM           297
# ... with 95 more rows
# i Use `print(n = ...)` to see more rows

You'll see that by default the values of dest are displayed in alphabetical order here. We are interested in finding those airports that appear most:

freq_dest %>% 
  arrange(num_flights)

# A tibble: 105 x 2
   dest  num_flights
   <chr>       <int>
 1 LEX             1
 2 LGA             1
 3 ANC             8
 4 SBN            10
 5 HDN            15
 6 MTJ            15
 7 EYW            17
 8 PSP            19
 9 JAC            25
10 BZN            36
# ... with 95 more rows
# i Use `print(n = ...)` to see more rows

This is actually giving us the opposite of what we are looking for. It tells us the least frequent destination airports first. To switch the ordering to be descending instead of ascending we use the desc (descending) function:

freq_dest %>% 
  arrange(desc(num_flights))

# A tibble: 105 x 2
   dest  num_flights
   <chr>       <int>
 1 ORD         17283
 2 ATL         17215
 3 LAX         16174
 4 BOS         15508
 5 MCO         14082
 6 CLT         14064
 7 SFO         13331
 8 FLL         12055
 9 MIA         11728
10 DCA          9705
# ... with 95 more rows
# i Use `print(n = ...)` to see more rows