simple nested functions and dplyr tidyeval - r

Question

library(tidyverse)
set.seed(1)
graph.data <- tibble(cal.date = as.Date(40100:40129, origin = "1899-12-30"),
random_num = rnorm(30, 8, 5))
This is the data frame we're working with here.
# A tibble: 30 x 2
cal.date random_num
<date> <dbl>
1 2009-10-14 4.87
2 2009-10-15 8.92
3 2009-10-16 3.82
4 2009-10-17 16.0
5 2009-10-18 9.65
6 2009-10-19 3.90
7 2009-10-20 10.4
8 2009-10-21 11.7
9 2009-10-22 10.9
10 2009-10-23 6.47
# ... with 20 more rows
I'm trying to nest(sp? lexical scope) two functions, which I call child_function and parent_function.
child_function <- function(df, variable, hor.line = 6) {
variable <- enquo(variable)
df <- mutate(mutation = 2 * !!variable, horizontal.line = hor.line)
}
parent_function <- function(df, date, variable, hor.line = 6) {
date <- enquo(date)
variable <- enquo(variable)
hor.line <- enquo(hor.line)
df <- child_function(df, !!variable, !!hor.line) %>% print()
p <- ggplot(df, aes(date, mutation)) +
geom_point() +
geom_hline(aes(yintercept = !!hor.line))
p
}
When I test it all out with the line below I get "Error in !variable : invalid argument type".
parent_function(graph.data, date = cal.date, variable = random_num, hor.line=8)
I imagine I'm not using the proper dplyr tidyeval syntax. What's wrong with my functions?

Answer 1

Needed a bit of a cleanup, but now it should work:
library(tidyverse)
set.seed(1)
graph.data <- tibble(cal.date = as.Date(40100:40129, origin = "1899-12-30"),
random_num = rnorm(30, 8, 5))
child_function <- function(df, variable, hor.line = 6) {
variable <- enquo(variable)
df <- mutate(df, mutation := 2 * !! variable, horizontal.line := hor.line)
}
parent_function <- function(df, date, variable, hor.line = 6) {
date <- enquo(date)
variable <- enquo(variable)
df <- child_function(df, !! variable, hor.line) %>% print()
p <- ggplot(df, aes(!! date, mutation)) +
geom_point() +
geom_hline(aes(yintercept = hor.line))
p
}
parent_function(graph.data, date = cal.date, variable = random_num, hor.line=8)
I think the main issue was that sometimes you put !! or enquo where there was no need and vice versa.