Cross Join in dplyr in R

Question

library(dplyr)
cust_time<-data.frame(cid=c(\"c1\",\"c2\",\"c3\",\"c4\",\"c5\"),ts=c(2,7,11,13,17))
#I want to do a cross join on self, preferable in dplyr else ba         


        

Answer 1

Here's a solution that is completely dplyr-compatible. It shares many of the same ideas as attitude_stool's solution but has the advantage of only being one line.

require(magrittr)  # for the %<>% operator

# one line:
(cust_time %<>% mutate(foo = 1)) %>% 
        full_join(cust_time, by = 'foo') %>% 
        select(-foo)

Answer 2

As of dplyr version 1.0, you can do a cross join by specifying by = character():

cust_time %>% full_join(cust_time, by = character())

Answer 3

You just need a dummy column to join on:

cust_time$k <- 1
cust_time %>% 
  inner_join(cust_time, by='k') %>%
  select(-k)

Or if you don't want to modify your original dataframe:

cust_time %>%
  mutate(k = 1) %>%
  replicate(2, ., simplify=FALSE) %>%
  Reduce(function(a, b) inner_join(a, b, by='k'), .) %>%
  select(-k)