geom_lasso

# Inspired by Nadieh Bremer's lasso annotations here: https://twitter.com/NadiehBremer/status/1277622602735865856
# h/t Cedric Scherer: https://twitter.com/CedScherer/status/1278351840074240001


library(ggplot2); library(ggforce)

add_lasso_layer <- function(x1, x2, y) {
  width = x2 - x1
  space = width * 0.05
  lasso_points = data.frame(
    x = c(x1, x1-space, x1-space, x1+width/2, x2-width/2, x2+space, x2+space, x2),
    y = c(y, y - space/10,rep(y-space, 4), y - space/10, y),
    id = rep(1:2, each = 4))
  list(ggforce::geom_bezier(data = lasso_points, aes(x = x, y = y, group = id)),
       geom_segment(aes(x = x2 + space*0.45, xend = x2 + width/2,
                        y = y - space/6, yend = y - space/6)))
}

ggplot() +
  geom_tile(aes(x = 0, y = 0, width = 2, height = 2), fill = "wheat") +
  add_lasso_layer(-1, 1, 0) +
  coord_equal() +
  theme_void()