hatch.r

require(ggplot2)

library(gridSVG)
library(grid)

plotCoords <- read.csv("http://eborbath.github.io/stackoverflow/PlotCoords.csv")
showCoords <- read.csv("http://eborbath.github.io/stackoverflow/showCoords.csv")


GeomHatch <- ggproto("GeomHatch", GeomPolygon,
                     required_aes = c("x", "y"),
                     default_aes = aes(colour = NA, fill = NA, size = 0.5, linetype = 1,
                                       alpha = NA),
                     
                     draw_panel = function(data, panel_params, coord) {
                       n <- nrow(data)
                       if (n == 1) return(zeroGrob())
                       
                       munched <- coord_munch(coord, data, panel_params)
                       # Sort by group to make sure that colors, fill, etc. come in same order
                       munched <- munched[order(munched$group), ]
                       
                       # For gpar(), there is one entry per polygon (not one entry per point).
                       # We'll pull the first value from each group, and assume all these values
                       # are the same within each group.
                       first_idx <- !duplicated(munched$group)
                       first_rows <- munched[first_idx, ]
                       
                       gl <- by(munched, munched$group, function(m){
                         
                         g <- polygonGrob(m$x, m$y, default.units = "native")
                         patternFillGrob(g, pattern = pattern(linesGrob(gp=gpar(col="red",lwd=3)),
                                                              width = unit(2, "mm"), height = unit(2, "mm"),
                                                              dev.width = 1, dev.height = 1))
                       }, simplify = FALSE)
                       gTree(children = do.call(gList, gl))
                       
                     }
)

geom_hatch <- function(mapping = NULL, data = NULL, stat = "identity",
                       position = "identity", na.rm = FALSE, show.legend = NA, 
                       inherit.aes = TRUE, ...) {
  layer(
    geom = GeomHatch, mapping = mapping,  data = data, stat = stat, 
    position = position, show.legend = show.legend, inherit.aes = inherit.aes,
    params = list(na.rm = na.rm, ...)
  )
}


p <- ggplot() +
  geom_hatch(
    data = plotCoords,
    aes(x = long, y = lat, group = group),
    fill = NA, colour = NA, size = 0.6) +
  geom_polygon(
    data = showCoords,
    aes(x = long, y = lat, group = group),
    fill = "grey", colour = "black", size = 0.6) +
  geom_polygon(
    data = showCoords,
    aes(x = long, y = lat, group = group, fill = sh_left),
    colour = "black", size = 0.1) +
  scale_fill_gradient(
    low = "gray90", high = "gray0",
    name = "Share of left-wing protesters",
    guide = guide_colorbar(
      direction = "horizontal",
      barheight = unit(2, units = "mm"),
      barwidth = unit(50, units = "mm"),
      draw.ulim = F,
      title.position = 'top',
      title.hjust = 0.5,
      label.hjust = 0.5
    )) +
  scale_x_continuous(element_blank(), breaks = NULL) +
  scale_y_continuous(element_blank(), breaks = NULL) +
  coord_map(xlim = c(-26, 47),  ylim = c(32.5, 73)) + 
  theme_bw() +
  theme(legend.justification = c(-0.4, 1.2), legend.position = c(0, 1))

grid.newpage()
grid.draw(grid.force(ggplotGrob(p)))
grid.export("test.svg", rootAttrs = c(width=1000,height=1000,viewBox="0 0 1000 1000"))