cartesian product with dplyr R

I'm trying to find the dplyr function for cartesian product. I've two simple data.frame with no common variable:

x <- data.frame(x=c("a","b","c"))
y <- data.frame(y=c(1,2,3))

I would like to reproduce the result of

merge(x,y)

  x y
1 a 1
2 b 1
3 c 1
4 a 2
5 b 2
6 c 2
7 a 3
8 b 3
9 c 3

I've already looked for this (for example here or here) without finding anything useful.

Thank you very much

Use crossing from the tidyr package:

x <- data.frame(x=c("a","b","c"))
y <- data.frame(y=c(1,2,3))

crossing(x, y)

Result:

   x y
 1 a 1
 2 a 2
 3 a 3
 4 b 1
 5 b 2
 6 b 3
 7 c 1
 8 c 2
 9 c 3

Apologies to all: the below example does not appear to work with data.frames or data.tables.

When x and y are database tbls (tbl_dbi / tbl_sql) you can now also do:

full_join(x, y, by = character())

Added to dplyr at the end of 2017, and also gets translated to a CROSS JOIN in the DB world. Saves the nastiness of having to introduce the fake variables.

If we need a tidyverse output, we can use expand from tidyr

library(tidyverse)
y %>% 
   expand(y, x= x$x) %>%
   select(x,y)
# A tibble: 9 × 2
#       x     y
#  <fctr> <dbl>
#1      a     1
#2      b     1
#3      c     1
#4      a     2
#5      b     2
#6      c     2
#7      a     3
#8      b     3
#9      c     3

When faced with this problem, I tend to do something like this:

x <- data.frame(x=c("a","b","c"))
y <- data.frame(y=c(1,2,3))
x %>% mutate(temp=1) %>% 
inner_join(y %>% mutate(temp=1),by="temp") %>%
dplyr::select(-temp) 

If x and y are multi-column data frames, but I want to do every combination of a row of x with a row of y, then this is neater than any expand.grid() option that I can come up with