zapwap.R

# devtools::install_github("romainfrancois/zap")
library(dplyr)
#> 
#> Attaching package: 'dplyr'
#> The following objects are masked from 'package:stats':
#> 
#>     filter, lag
#> The following objects are masked from 'package:base':
#> 
#>     intersect, setdiff, setequal, union
library(zap)
library(purrr)

starwars <- head(starwars)


# wap is like pmap, but it makes it easier to refer to the 
# columns by their name
starwars %>% 
  wap(~ length(films)) 
#> [[1]]
#> [1] 5
#> 
#> [[2]]
#> [1] 6
#> 
#> [[3]]
#> [1] 7
#> 
#> [[4]]
#> [1] 4
#> 
#> [[5]]
#> [1] 5
#> 
#> [[6]]
#> [1] 3

# creates a list of length 1 integer vectors
starwars %>% 
  wap_int(~ length(films)) 
#> [1] 5 6 7 4 5 3

# instead of e.g.
starwars %>% 
  pull(films) %>% 
  map_int(~ length(.x))
#> [1] 5 6 7 4 5 3


starwars %>% 
  zap_int(n = ~ length(films)) %>% 
  zap_dfr(x = ~ data.frame(vehicles = length(vehicles), starships = length(starships))) %>% 
  select(1:2, n, x)
#> # A tibble: 6 x 4
#>   name           height     n x$vehicles $starships
#>   <chr>           <int> <int>      <int>      <int>
#> 1 Luke Skywalker    172     5          2          2
#> 2 C-3PO             167     6          0          0
#> 3 R2-D2              96     7          0          0
#> 4 Darth Vader       202     4          0          1
#> 5 Leia Organa       150     5          1          0
#> 6 Owen Lars         178     3          0          0

# instead of something like this
# (:scream: dplyr::mutate does not yet handle returning data frames from mutate)
starwars %>% 
  mutate(n = map_int(films, length)) %>% 
  tibble::add_column(x = pmap_dfr(
    list(.$vehicles, .$starships), 
    ~data.frame(vehicles = length(.x), starships = length(.y))
  )) %>% 
  select(1:2, n, x)
#> # A tibble: 6 x 4
#>   name           height     n x$vehicles $starships
#>   <chr>           <int> <int>      <int>      <int>
#> 1 Luke Skywalker    172     5          2          2
#> 2 C-3PO             167     6          0          0
#> 3 R2-D2              96     7          0          0
#> 4 Darth Vader       202     4          0          1
#> 5 Leia Organa       150     5          1          0
#> 6 Owen Lars         178     3          0          0