library(apexcharter)

# On scatter chart
apex(
  data = iris,
  aes(Sepal.Length, Sepal.Width),
  "scatter"
) %>% 
  add_point(
    x = mean(iris$Sepal.Length),
    y = mean(iris$Sepal.Width)
  )

# Some options
apex(
  data = iris,
  aes(Sepal.Length, Sepal.Width),
  "scatter"
) %>% 
  add_point(
    x = mean(iris$Sepal.Length),
    y = mean(iris$Sepal.Width), 
    fill = "firebrick",
    color = "firebrick",
    size = 8,
    label = label(text = "Mean", offsetY = 0)
  )


# Several points
clusters <- kmeans(iris[, 1:2], 3)
apex(
  data = iris,
  aes(Sepal.Length, Sepal.Width),
  "scatter"
) %>% 
  add_point(
    x = clusters$centers[, 1],
    y = clusters$centers[, 2]
  )