Melts all numeric columns of df into a single long
format and draws them as side-by-side horizontal boxplots on one plot.
Non-numeric columns are silently dropped.
Examples
vector <- generate_missing(rnorm(50), missing = 10)
df <- generate_missing(mtcars[, 1:2], missing = 10)
plot_boxplot(df = vector)
plot_boxplot(df = df)