Pointwise mutual information of pairs of items

Find pointwise mutual information of pairs of items in a column, based on a "feature" column that links them together. This is an example of the spread-operate-retidy pattern.

Usage

pairwise_pmi(tbl, item, feature, sort = FALSE, ...)

pairwise_pmi_(tbl, item, feature, sort = FALSE, ...)

Arguments

tbl: Table
item: Item to compare; will end up in item1 and item2 columns
feature: Column describing the feature that links one item to others
sort: Whether to sort in descending order of the pointwise mutual information
...: Extra arguments passed on to squarely, such as diag and upper

Value

A tbl_df with three columns, item1, item2, and pmi.

Examples


library(dplyr)

dat <- tibble(group = rep(1:5, each = 2),
              letter = c("a", "b",
                         "a", "c",
                         "a", "c",
                         "b", "e",
                         "b", "f"))

# how informative is each letter about each other letter
pairwise_pmi(dat, letter, group)
#> # A tibble: 8 × 3
#>   item1 item2    pmi
#>   <chr> <chr>  <dbl>
#> 1 b     a     -0.588
#> 2 c     a      0.511
#> 3 a     b     -0.588
#> 4 e     b      0.511
#> 5 f     b      0.511
#> 6 a     c      0.511
#> 7 b     e      0.511
#> 8 b     f      0.511
pairwise_pmi(dat, letter, group, sort = TRUE)
#> # A tibble: 8 × 3
#>   item1 item2    pmi
#>   <chr> <chr>  <dbl>
#> 1 c     a      0.511
#> 2 e     b      0.511
#> 3 f     b      0.511
#> 4 a     c      0.511
#> 5 b     e      0.511
#> 6 b     f      0.511
#> 7 b     a     -0.588
#> 8 a     b     -0.588