1 Setup
library(tidyverse) # data wrangling
library(easystats) # comfort in statsdata(mtcars)In essence, we want to build this kind of plot programmatically:
mtcars %>%
ggplot(aes(x=hp)) +
geom_histogram()
2 Let’s go
2.1 Way 1
Let’s use unquoted variable names.
plot_descriptives0 <- function(data, var) {
data %>%
ggplot(aes(x = {{var}})) +
geom_histogram()
}
plot_descriptives0(mtcars, hp)
2.2 Way 2
Somewhat more elaborated, but same idea:
plot_descriptives1 <- function(data, var, group) {
var_string <- deparse(substitute(var))
data %>%
select({{var}}, {{group}}) %>%
drop_na() %>%
group_by({{group}}) %>%
mutate({{group}} := as.factor({{group}})) %>%
describe_distribution(iqr = FALSE, range = TRUE, quartiles = TRUE) %>%
select(Variable, Mean, SD, .group) %>%
mutate(group = str_remove(.group, "^.+=")) %>%
select(-.group) %>%
#pivot_longer(-c(Variable, group)) %>%
ggplot(aes(x = group)) +
geom_errorbar(aes(ymin = Mean-(2*SD), ymax = Mean+(2*SD)), width = .1) +
geom_point2(aes(y = Mean), alpha = .7, size = 3) +
facet_wrap(~ Variable) +
labs(caption = "Error bars show mean ± 2SD",
title = paste0("Variable: ", var_string)) +
coord_flip() +
theme(legend.position = "bottom")
}plot_descriptives1(mtcars, hp, cyl)
This line gives us the variable name as a string:
deparse(substitute(var))
#> [1] "var"More specifically:
deparse(substitute(mtcars$hp))
#> [1] "mtcars$hp"2.3 Way 2
This time, we have variables as strings
plot_descriptives2 <- function(data, var) {
data %>%
ggplot(aes_string(x = var)) +
geom_histogram() +
labs(title = paste0("Variable: ", var))
}However, aes_string is deprecated.
plot_descriptives2(mtcars, "hp")
2.4 Way 3
Here we use sym
?sym
#> Help on topic 'sym' was found in the following packages:
#>
#> Package Library
#> rlang /Users/sebastiansaueruser/Rlibs
#> dplyr /Users/sebastiansaueruser/Rlibs
#> ggplot2 /Users/sebastiansaueruser/Rlibs
#>
#>
#> Using the first match ...sym() and syms() take strings as input and turn them into symbols.
See:
sym("hp")
#> hp!! is used to evaluate a symbol, ie., gives back the “real” column, such as hp.
The !! operator unquotes its argument. It gets evaluated immediately in the surrounding context.
plot_descriptives3 <- function(data, var) {
var_enquo <- sym(var)
data %>%
ggplot(aes(x = !!var_enquo)) +
geom_histogram()
}
plot_descriptives3(mtcars, "hp")
2.5 Way 4
We can swqp the “bang-bang” !! in favor of “curly-curly” :
plot_descriptives4 <- function(data, var) {
var_enquo <- sym(var)
data %>%
ggplot(aes(x = {{var_enquo}})) +
geom_histogram()
}
plot_descriptives4(mtcars, "hp")
3 Further reading
There are many sources, here are some:
4 Reproducibility
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