r - make plotting function with ggplot2, aes_string and reorder - r

Question

I'm trying to make a function that will use ggplot2inside,aes_stringand reorder but with no luck so far.
Basically if we have a sample dataset like the following:
library(ggplot2)
library(dplyr)
set.seed(123)
dt <- data.frame(
id = c(1,1,1,2,2),
a = c("b", "d", "c", "a", "b"),
b = sample(1:10, 5, replace = F),
cat = c(1,1,2,2,2)) %>%
mutate(a = as.factor(a)) %>%
as_tibble()
I want the function to accept the following arguments: the dataset, a filtering variable, and two variables for plotting.
This is what I managed to do:
myplot <- function(df, filtval, var1, var2) {
data <- df %>% filter(id == filtval)
ggplot(data) +
geom_point(
aes_string(
x = reorder(var1, var2),
y = var2)
)
}
Unfortunately when running it returns the error:
myplot(dt, 1, "a", "b")
Warning message:
In mean.default(X[[i]], ...) :
argument is not numeric or logical: returning NA
This is what I want the function to do:
data <- dt %>% filter(id == 1)
ggplot(data) +
geom_col(aes(x = reorder(a, - b), y = b))

Answer 1

With the latest version of ggplot, you should be use aes with !! and sym() to turn your strings into symbols.
myplot <- function(df, filtval, var1, var2) {
data <- df %>% filter(id == filtval)
ggplot(data) +
geom_point(
aes(
x = reorder(!!sym(var1), !!sym(var2)),
y = !!sym(var2))
)
}

Answer 2

After discussing with mr Flick (see below), this should do NOT be used:
myplot <- function(df, filtval, var1, var2) {
data <- df %>% filter(id == filtval)
data$new_order <- reorder(data[[var1]], data[[var2]])
ggplot(data) +
geom_point(mapping=
aes_string(
x = "new_order",
y = var2)
)
}
Take his solution instead :)