You will need to define a method for this method if you want to extend
ggplot2 to handle new types of data. If you simply want to pass the vector
through as an additional aesthetic, return "identity".
Value
A character vector of scale types. These will be tried in turn
to find a default scale. For example, if scale_type() returns
c("foo", "bar") and the vector is used with the colour aesthetic,
ggplot2 will first look for scale_colour_foo then
scale_colour_bar.
Examples
scale_type(1:5)
#> [1] "continuous"
scale_type("test")
#> [1] "discrete"
scale_type(Sys.Date())
#> [1] "date" "continuous"