How to pass a list of bare elements to a tidyeval plot function that accepts bare elements to purrr map

Question

Given the following type of function:

library(tidyverse)

make_plot <- function(var) {
  quo_var <- enquo(var)
  ggplot(mtcars, aes(x = !!quo_var, y = mpg)) +
    geom_point()
}

I would like to call this on various columns of a data.frame like this:

make_plot(hp)
make_plot(am)
...

But to keep the code DRY, I would like to use purrr::map or purrr::walk, but the following does not work:

list(hp, am) %>%
  map(make_plot)

I have also tried list("hp", "am") %>% map(make_plot(sym(.)) which also does not work. What is the correct approach here for using a list of strings or variables?

You need `alist()` instead of `list()`. See also this https://stackoverflow.com/a/49834499/786542 — Tung, Apr 03 '19 at 17:24

akrun · Accepted Answer · 2019-04-03T17:03:53.883

2

We can wrap with quote to avoid the early evaluation

library(tidyverse)
library(ggplot2)
list(quote(hp), quote(am)) %>% 
      map(make_plot)

Or another option is to pass it as list of quosure (quos)

quos(hp, am) %>%
    map(make_plot)

-last plot

To make the ~ .x work, do an evaluation with !!

quos(hp, am) %>%
            walk(~ print(make_plot(!! .x)))

edited Apr 03 '19 at 17:03

answered Apr 03 '19 at 16:13

akrun

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Do you know why `quos(hp, am) %>% walk(~ print(make_plot(.)))` fails? – JasonAizkalns Apr 03 '19 at 17:01
1

@JasonAizkalns You can use `!!`. updated the post (to evaluate the `.x` instead of directly parsing the literal .x – akrun Apr 03 '19 at 17:04

How to pass a list of bare elements to a tidyeval plot function that accepts bare elements to purrr map

1 Answers1