Add custom objects to ggplot — update

This generic allows you to add your own methods for adding custom objects to a ggplot with +.gg. The ggplot_add() function is vestigial and the update_ggplot() function should be used instead.

Usage

update_ggplot(object, plot, ...)

ggplot_add(object, plot, ...)

Arguments

object: An object to add to the plot
plot: The ggplot object to add object to

Value

A modified ggplot object

Details

Custom methods for update_ggplot() are intended to update the plot variable using information from a custom object. This can become convenient when writing extensions that don't build on the pre-existing grammar like layers, facets, coords and themes. The update_ggplot() function is never intended to be used directly, but it is triggered when an object is added to a plot via the + operator. Please note that the full plot object is exposed at this point, which comes with the responsibility of returning the plot intact.

Examples

# making a new method for the generic
# in this example, we enable adding text elements
S7::method(update_ggplot, list(element_text, class_ggplot)) <-
  function(object, plot, ...) {
    plot + theme(text = object)
  }

# we can now use `+` to add our object to a plot
ggplot(mpg, aes(displ, cty)) +
  geom_point() +
  element_text(colour = "red")


# clean-up