README.md

In romainfrancois/zap: rowwise operations on a data frame

rap

Experimenting with yet another way to do rowwise operations.

Installation

You can install rap from gitub

# install.packages("devtools")
devtools::install_github("romainfrancois/rap")

Why

This offers rap() as an alternative to some versions of:

• rowwise() + do()
• mutate() + pmap()
• maybe purrrlyr ?
• probably other approaches

rap() works with lambdas supplied as formulas, similar to purrr::map() but instead of .x, .y, ..1, ..2, ...the lambda can use the column names, which stand for a single element of the associated vector, in the [[ sense.

rap

library(tidyverse)
#> ── Attaching packages ──────────────────── tidyverse 1.2.1 ──
#> ✔ ggplot2 3.1.0           ✔ purrr   0.2.5.9000 
#> ✔ tibble  1.4.99.9006     ✔ dplyr   0.7.8      
#> ✔ tidyr   0.8.1           ✔ stringr 1.3.1      
#> ✔ readr   1.1.1           ✔ forcats 0.3.0
#> ── Conflicts ─────────────────────── tidyverse_conflicts() ──
#> ✖ dplyr::filter() masks stats::filter()
#> ✖ dplyr::lag()    masks stats::lag()
library(rap)

tbl <- tibble(cyl_threshold = c(4, 6, 8), mpg_threshold = c(30, 25, 20)) 
tbl
#> # A tibble: 3 x 2
#>   cyl_threshold mpg_threshold
#>           <dbl>         <dbl>
#> 1             4            30
#> 2             6            25
#> 3             8            20

tbl %>% 
  rap(x = ~filter(mtcars, cyl == cyl_threshold, mpg < mpg_threshold))
#> # A tibble: 3 x 3
#>   cyl_threshold mpg_threshold x                     
#>           <dbl>         <dbl> <list>                
#> 1             4            30 <data.frame [7 × 11]> 
#> 2             6            25 <data.frame [7 × 11]> 
#> 3             8            20 <data.frame [14 × 11]>

If the lhs of the formula is empty, rap() adds a list column. Otherwise the lhs can be used to specify the type:

tbl %>% 
  rap(
    x =           ~ filter(mtcars, cyl == cyl_threshold, mpg < mpg_threshold), 
    n = integer() ~ nrow(x)
  )
#> # A tibble: 3 x 4
#>   cyl_threshold mpg_threshold x                          n
#>           <dbl>         <dbl> <list>                 <int>
#> 1             4            30 <data.frame [7 × 11]>      7
#> 2             6            25 <data.frame [7 × 11]>      7
#> 3             8            20 <data.frame [14 × 11]>    14

this example is based on this issue, which has equivalent with pmap:

tbl %>%
  mutate(
    x = pmap(
      .l = list(cyl_threshold, mpg_threshold),
      function(cc, mm) filter(mtcars, cyl == cc, mpg < mm)
    ), 
    n = map_int(x, nrow)
  )
#> # A tibble: 3 x 4
#>   cyl_threshold mpg_threshold x                          n
#>           <dbl>         <dbl> <list>                 <int>
#> 1             4            30 <data.frame [7 × 11]>      7
#> 2             6            25 <data.frame [7 × 11]>      7
#> 3             8            20 <data.frame [14 × 11]>    14

wap

library(dplyr)

starwars <- head(starwars)

# creates a list of length 1 integer vectors
# because type not specified
starwars %>% 
  wap(~length(films)) 
#> [[1]]
#> [1] 5
#> 
#> [[2]]
#> [1] 6
#> 
#> [[3]]
#> [1] 7
#> 
#> [[4]]
#> [1] 4
#> 
#> [[5]]
#> [1] 5
#> 
#> [[6]]
#> [1] 3

# using the lhs to specify the type
starwars %>% 
  wap(integer() ~ length(films))
#> [1] 5 6 7 4 5 3

# list of data frames
starwars %>% 
  wap(~ data.frame(vehicles = length(vehicles), starships = length(starships)))
#> [[1]]
#>   vehicles starships
#> 1        2         2
#> 
#> [[2]]
#>   vehicles starships
#> 1        0         0
#> 
#> [[3]]
#>   vehicles starships
#> 1        0         0
#> 
#> [[4]]
#>   vehicles starships
#> 1        0         1
#> 
#> [[5]]
#>   vehicles starships
#> 1        1         0
#> 
#> [[6]]
#>   vehicles starships
#> 1        0         0

# Specify type as data.frame() row binds them
starwars %>% 
  wap(data.frame() ~ data.frame(vehicles = length(vehicles), starships = length(starships)))
#>   vehicles starships
#> 1        2         2
#> 2        0         0
#> 3        0         0
#> 4        0         1
#> 5        1         0
#> 6        0         0

zest_join

🍋 zest_join() is similar to dplyr::nest_join() but you control what goes in the nested column. Z is N but ⤵️.

tbl <- tibble(cyl_threshold = c(4, 6, 8), mpg_threshold = c(30, 25, 20)) 
tbl %>%
  zest_join(mtcars, data = ~cyl == !!cyl_threshold & mpg < !!mpg_threshold)
#> # A tibble: 3 x 3
#>   cyl_threshold mpg_threshold data                  
#>           <dbl>         <dbl> <list>                
#> 1             4            30 <data.frame [7 × 11]> 
#> 2             6            25 <data.frame [7 × 11]> 
#> 3             8            20 <data.frame [14 × 11]>

In the rhs of the formula :

• cyl and mpg refer to columns of mtcars
• cyl_threshold and mpg_threshold refer to the current value from tbl because these columns don't exist in mtcars. If you wanted to refer to columns that are present both in mtcars and tbl you would have to unquote the columns in tbl with the unquoting operator, e.g. !!cyl

romainfrancois/zap documentation built on June 9, 2019, 12:41 p.m.