In romainfrancois/rap: rowwise operations on a data frame

knitr::opts_chunk$set(
  collapse = TRUE,
  comment = "#>",
  fig.path = "man/figures/README-",
  out.width = "100%"
)

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)
library(rap)

tbl <- tibble(cyl_threshold = c(4, 6, 8), mpg_threshold = c(30, 25, 20)) 
tbl

tbl %>% 
  rap(x = ~filter(mtcars, cyl == cyl_threshold, mpg < mpg_threshold))

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)
  )

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)
  )

wap

library(dplyr)

starwars <- head(starwars)

# creates a list of length 1 integer vectors
# because type not specified
starwars %>% 
  wap(~length(films)) 

# using the lhs to specify the type
starwars %>% 
  wap(integer() ~ length(films))

# list of data frames
starwars %>% 
  wap(~ data.frame(vehicles = length(vehicles), starships = length(starships)))

# Specify type as data.frame() row binds them
starwars %>% 
  wap(data.frame() ~ data.frame(vehicles = length(vehicles), starships = length(starships)))

zest_join

r emo::ji("lemon") zest_join() is similar to dplyr::nest_join() but you control what goes in the nested column. Z is N but r emo::ji("arrow_heading_down").

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)

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/rap documentation built on June 8, 2019, 5:42 p.m.