R/geom_split_violin.R

In JanCoUnchained/ggunchained: ggplot visualisation shortcuts

#' Utility function that is used by geom_split_violin()
#' @export
#' @description TBA, taken from https://gist.github.com/Karel-Kroeze/746685f5613e01ba820a31e57f87ec87

GeomSplitViolin <- ggplot2::ggproto("GeomSplitViolin", ggplot2::GeomViolin,
                           draw_group = function(self, data, ..., draw_quantiles = NULL) {
                             data <- transform(data, xminv = x - violinwidth * (x - xmin), xmaxv = x + violinwidth * (xmax - x))
                             grp <- data[1, "group"]
                             newdata <- plyr::arrange(transform(data, x = if (grp %% 2 == 1) xminv else xmaxv), if (grp %% 2 == 1) y else -y)
                             newdata <- rbind(newdata[1, ], newdata, newdata[nrow(newdata), ], newdata[1, ])
                             newdata[c(1, nrow(newdata) - 1, nrow(newdata)), "x"] <- round(newdata[1, "x"])

                             if (length(draw_quantiles) > 0 & !scales::zero_range(range(data$y))) {
                               stopifnot(all(draw_quantiles >= 0), all(draw_quantiles <=
                                                                         1))
                               quantiles <- ggplot2:::create_quantile_segment_frame(data, draw_quantiles)
                               aesthetics <- data[rep(1, nrow(quantiles)), setdiff(names(data), c("x", "y")), drop = FALSE]
                               aesthetics$alpha <- rep(1, nrow(quantiles))
                               both <- cbind(quantiles, aesthetics)
                               quantile_grob <- GeomPath$draw_panel(both, ...)
                               ggplot2:::ggname("geom_split_violin", grid::grobTree(GeomPolygon$draw_panel(newdata, ...), quantile_grob))
                             }
                             else {
                               ggplot2:::ggname("geom_split_violin", GeomPolygon$draw_panel(newdata, ...))
                             }
                           })


#' Split violin plot
#' @description TBA, but it is very similar to geom_violin()
#'    Taken from https://gist.github.com/Karel-Kroeze/746685f5613e01ba820a31e57f87ec87
#' @export
#' @examples
#' ggplot(mtcars, aes(x = wt, y = mpg, colour = factor(gear))) +
#' geom_split_violin()

geom_split_violin <- function(mapping = NULL, data = NULL, stat = "ydensity", position = "identity", ...,
                              draw_quantiles = NULL, trim = TRUE, scale = "area", na.rm = FALSE,
                              show.legend = NA, inherit.aes = TRUE) {
  layer(data = data, mapping = mapping, stat = stat, geom = GeomSplitViolin,
        position = position, show.legend = show.legend, inherit.aes = inherit.aes,
        params = list(trim = trim, scale = scale, draw_quantiles = draw_quantiles, na.rm = na.rm, ...))
}