Feature request: include 0s in pairwise output

[dhalpern]

I'm not totally sure if this is a feature or a bug but many pairwise comparisons drop 0s in the output. For instance, in the pairwise count example

dat <- data_frame(group = rep(1:5, each = 2),
                  letter = c("a", "b",
                             "a", "c",
                             "a", "c",
                             "b", "e",
                             "b", "f"))
count the number of times two letters appear together
pairwise_count(dat, letter, group, upper = FALSE)

The output only includes those with a count greater than 1

item1 item2     n
  <chr> <chr> <dbl>
1 a     b         1
2 a     c         2
3 b     e         1
4 b     f         1

It would be great to have an option to include all pairs of items. My actual use case is for having pairwise similarities of exactly 0 so it would be great to have that feature there as well.

[elsherbini]

Agreed that it'd be nice to have the pairwise_ family of functions not drop zeros. You could work around it in this case by using complete() https://tidyr.tidyverse.org/reference/complete.html

dat <- data_frame(group = rep(1:5, each = 2),
                  letter = c("a", "b",
                             "a", "c",
                             "a", "c",
                             "b", "e",
                             "b", "f"))
pairwise_count(dat, letter, group, upper = FALSE) %>%
  complete(item1, item2, fill=list(n=0))