How can I write dplyr groups to separate files?

Question

I'm trying to create separate .csv files for each group in a data frame grouped with dplyr's group_by function. So far I have something like

by_cyl <- group_by(mtcars, cyl)
do(by_cyl, write_csv(., "test.csv"))

As expected, this writes a single .csv file with only the data from the last group. How can I modify this to write multiple .csv files, each with filenames that include cyl?

Answer 1

With dplyr_0.8.0 this can be done with group_by_walk

library(dplyr)
library(readr)
mtcars %>%
   group_by(cyl) %>%
   group_walk(~ write_csv(.x, paste0(.y$cyl, "test.csv")))