R/Geom_flat_violin.R

In gfalbery/ggregplot:

library(ggplot2)
library(dplyr)


"%||%" <- function(a, b) {
  if (!is.null(a)) a else b
}

geom_flat_violin <- function(mapping = NULL, data = NULL, stat = "ydensity",
                             position = "dodge", trim = TRUE, scale = "area",
                             show.legend = NA, inherit.aes = TRUE, ...) {
  layer(
    data = data,
    mapping = mapping,
    stat = stat,
    geom = GeomFlatViolin,
    position = position,
    show.legend = show.legend,
    inherit.aes = inherit.aes,
    params = list(
      trim = trim,
      scale = scale,
      ...
    )
  )
}

#' @rdname ggplot2-ggproto
#' @format NULL
#' @usage NULL
#' @export
GeomFlatViolin <-
  ggproto("GeomFlatViolin", Geom,
          setup_data = function(data, params) {
            data$width <- data$width %||%
              params$width %||% (resolution(data$x, FALSE) * 0.9)
            
            # ymin, ymax, xmin, and xmax define the bounding rectangle for each group
            data %>%
              group_by(group) %>%
              mutate(ymin = min(y),
                     ymax = max(y),
                     xmin = x,
                     xmax = x + width / 2)
          },
  
  draw_group = function(data, panel_scales, coord) {
    # Find the points for the line to go all the way around
    data <- transform(data, xminv = x,
                      xmaxv = x + violinwidth * (xmax - x))
    
    # Make sure it's sorted properly to draw the outline
    newdata <- rbind(plyr::arrange(transform(data, x = xminv), y),
                     plyr::arrange(transform(data, x = xmaxv), -y))
    
    # Close the polygon: set first and last point the same
    # Needed for coord_polar and such
    newdata <- rbind(newdata, newdata[1,])
    
    ggplot2:::ggname("geom_flat_violin", GeomPolygon$draw_panel(newdata, panel_scales, coord))
  },
  
  draw_key = draw_key_polygon,
  
  default_aes = aes(weight = 1, colour = "grey20", fill = "white", size = 0.5,
                    alpha = NA, linetype = "solid"),
  
  required_aes = c("x", "y")
  )