Extracting only those rows with a unique combination of column values in R

Question

I have a flight database giving route details and looks like this

Ori.  Dest  Carr. Pass Flights
JFK   LAX   Delta 15004 50
JFK   LAX   JetBl 17434 100
JFK   BOS   Delta 15344 89
ATL   FLR   AmerA 25054 90
OHD   LAX   Delta 19876 95
OHD   LAX   AmerA 12344 45

For output, I only need routes which have only 1 carrier The output should look like this -

JFK   BOS   Delta 15344 89
ATL   FLR   AmerA 25054 90

How to do this in R?

Answer 1

You can use:

library(dplyr)
df %>% group_by(Ori., Dest) %>% filter(n() == 1)

# Ori.  Dest  Carr.  Pass Flights
#  <chr> <chr> <chr> <int>   <int>
#1 JFK   BOS   Delta 15344      89
#2 ATL   FLR   AmerA 25054      90

Using data.table a

library(data.table)
setDT(df)[, .SD[.N == 1], .(Ori., Dest)]

and base R:

subset(df, ave(Flights, Ori., Dest, FUN = length) == 1)

data

df <- structure(list(Ori. = c("JFK", "JFK", "JFK", "ATL", "OHD", "OHD"
), Dest = c("LAX", "LAX", "BOS", "FLR", "LAX", "LAX"), Carr. = c("Delta", 
"JetBl", "Delta", "AmerA", "Delta", "AmerA"), Pass = c(15004L, 
17434L, 15344L, 25054L, 19876L, 12344L), Flights = c(50L, 100L, 
89L, 90L, 95L, 45L)), class = "data.frame", row.names = c(NA, -6L))

Answer 2

We can do this without any group by operation in base R

df[!(duplicated(df[1:2])|duplicated(df[1:2], fromLast = TRUE)),]
#  Ori. Dest Carr.  Pass Flights
#3  JFK  BOS Delta 15344      89
#4  ATL  FLR AmerA 25054      90

data

df <- structure(list(Ori. = c("JFK", "JFK", "JFK", "ATL", "OHD", "OHD"
), Dest = c("LAX", "LAX", "BOS", "FLR", "LAX", "LAX"), Carr. = c("Delta", 
"JetBl", "Delta", "AmerA", "Delta", "AmerA"), Pass = c(15004L, 
17434L, 15344L, 25054L, 19876L, 12344L), Flights = c(50L, 100L, 
89L, 90L, 95L, 45L)), class = "data.frame", row.names = c(NA, -6L))