R / ggplot2：在山脊线图中添加直接标签

Question

我正在尝试将directlabels添加到ggridges创建的山脊线图中。似乎directlabels不知道将标签应用于什么。可以指定这个吗？还是两个软件包不兼容？

# does not work
ggplot2::ggplot(iris,
                ggplot2::aes(x = Sepal.Length, y = Species, height = Sepal.Width)) +
  ggridges::geom_density_ridges(stat = "identity") +
  directlabels::direct.label("first.points")

Error in UseMethod("direct.label") : 
  no applicable method for 'direct.label' applied to an object of class "character"

# does not work
ggplot2::ggplot(iris,
                ggplot2::aes(x = Sepal.Length, y = Species, height = Sepal.Width)) +
  ggridges::geom_density_ridges(stat = "identity") +
  directlabels::direct.label.ggplot("first.points")

Error: $ operator is invalid for atomic vectors