R/geom_segment_straight.R

In ggpolar: Dots and Their Connections in Polar Coordinate System

# https://stackoverflow.com/questions/66196451/draw-straight-line-between-any-two-point-when-using-coord-polar-in-ggplot2-r
geom_segment_straight <- function(...) {
  layer <- geom_segment(...)
  new_layer <- ggproto(NULL, layer)
  old_geom <- new_layer$geom
  geom <- ggproto(
    NULL, old_geom,
    draw_panel = function(data, panel_params, coord,
                          arrow = NULL, arrow.fill = NULL,
                          lineend = "butt", linejoin = "round",
                          na.rm = FALSE) {
      data <- remove_missing(
        data,
        na.rm = na.rm, c(
          "x", "y", "xend", "yend",
          "linetype", "linewidth", "size", "shape"
        )
      )
      if (empty(data)) {
        return(zeroGrob())
      }
      coords <- coord$transform(data, panel_params)
      # xend and yend need to be transformed separately, as coord doesn't understand
      ends <- transform(data, x = xend, y = yend)
      ends <- coord$transform(ends, panel_params)

      arrow.fill <- if (!is.null(arrow.fill)) arrow.fill else coords$colour
      return(grid::segmentsGrob(
        coords$x, coords$y, ends$x, ends$y,
        default.units = "native", gp = grid::gpar(
          col = alpha(coords$colour, coords$alpha),
          fill = alpha(arrow.fill, coords$alpha),
          lwd = (coords$linewidth %||% coords$size) * .pt,
          lty = coords$linetype,
          lineend = lineend,
          linejoin = linejoin
        ),
        arrow = arrow
      ))
    }
  )
  new_layer$geom <- geom
  return(new_layer)
}

utils::globalVariables(
  c("xend", "yend")
)