R ggplot - box plot in generalzied function - r

Question

With ggplot I'm trying to make a custom function to plot boxplot for a single column in a dataframe such that it can be used with any dataframe
Specific Example
male = data.frame(male = c(127,44,28,83,0,6,78,6,5,213,73,20,214,28,11)) # data from
ggplot(data = male, aes(x = "", y = male)) + geom_boxplot() +
stat_summary(fun=mean, geom="point", shape=20, size=2, color="red", fill="red")
This gives the expected boxplot with the mean shown as a point.
Generalized function - here the operation done in the specific example is wrapped into a generalized function
boxPlotFn = function (df, colName) {
ggplot(data = df, aes_string(x = "", y = colName)) + geom_boxplot() +
stat_summary(fun=mean, geom="point", shape=20, size=2, color="red", fill="red")
}
And I call the function like below
boxPlotFn(male, "male")
However, this gives the error Error: No expression to parse - rlang::last_error() indicates that the error is happening at the call to ggplot. What am I not doing right here?

Answer 1

That's a bit tricky but easily solved. To make your function work with aes_string you have to quote the "double quotes" mapped on x using e.g. single quotes. Additionally it should probably be data = df inside your function:
library(ggplot2)
male = data.frame(male = c(127,44,28,83,0,6,78,6,5,213,73,20,214,28,11)) # data from
boxPlotFn = function (df, colName) {
ggplot(data = df, aes_string(x = '""', y = colName)) +
geom_boxplot() +
stat_summary(fun=mean, geom="point", shape=20, size=2, color="red", fill="red")
}
boxPlotFn(male, "male")