Keep desired columns when using summarise - r

Question

I want to get the top 10 destinations, and also how many flights were made to these destinations. I am using summarise, and my problem is that summarise throws away all columns that a not mentioned in the summarise(..). I need to keep the column origin for later use.
library(tidyverse)
library(nycflights13)
flights %>%
group_by(dest) %>%
summarise(n = n()) %>%
arrange(desc(n)) %>% head(10)
Here is the result from the code above
# A tibble: 10 x 2
dest allFlights
<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
I think this is correct. But all I am missing, is another column that prints the origin
I was thinking about doing some a join to get the origin, but this doesn't make sense, as doing the join on this result set might not yield the correct flights.
I found this post: How to summarise all columns using group_by and summarise? but it was not helpful to me, as summarise is unable to find the columns I mention, that are not in its function.

Answer 1

When you sum the flights by destination, you are summing the total number of flights arriving in the destination city, which have many different origin cities. So it would not make sense for there to be a single value in the origin column here.
If you want, you could replace group_by(dest) with group_by(origin,dest). That would give you the top 10 pairs of origin-destination cities, which is a different output than in your question, but would retain the origin and destination columns for further analysis.
library(tidyverse)
library(nycflights13)
flights %>%
group_by(origin, dest) %>%
summarise(n = n()) %>%
arrange(desc(n)) %>% head(10)
output
# A tibble: 10 x 3
# Groups: origin [3]
origin dest n
<chr> <chr> <int>
1 JFK LAX 11262
2 LGA ATL 10263
3 LGA ORD 8857
4 JFK SFO 8204
5 LGA CLT 6168
6 EWR ORD 6100
7 JFK BOS 5898
8 LGA MIA 5781
9 JFK MCO 5464
10 EWR BOS 5327