Using Unicode plot symbols in ggplot2

unicode_ggplot2.R

#negative numbers for "symbol" will be interpreted as Unicode values.
#But you must use a fint that supprots the symbols you want.

dataset <- chain(1:16, expand.grid(x=., y=.), mutate(shape=seq_along(x)))

print(ggplot(dataset) + aes(x=x, y=y, shape=factor(shape))
 + geom_point()
 + discrete_scale("shape", "manual", name="shape", palette=function(x) -seq(0x25A0L, length=x))
 + theme(legend.position="none")
 )

grid.gedit("geom_point.points", gp=gpar(fontfamily="MS Gothic", fontsize=14))

##or using grobs to skip the first printing
grid.newpage()
gr <- ggplotGrob(ggplot(dataset) + aes(x=x, y=y, shape=factor(shape))
 + geom_point()
 + discrete_scale("shape", "manual", name="shape", palette=function(x) -seq(0x25A0L, length=x))
 + theme(legend.position="none")
                 )

#https://groups.google.com/d/msg/ggplot2/cnVDSyobPy4/5U8ky3FPtHwJ
editGtable <- function(gt, idx, ...) {
  if (is.character(idx))
    idx <- which(gt$layout$name == idx)
  gt$grobs[[idx]] <- editGrob(gt$grobs[[idx]], ...)
  gt
}
gr <- editGtable(gr, "panel", "geom_point.points", grep=TRUE, global=TRUE,
                 gp=gpar(fontfamily="MS Gothic", fontsize=14))
grid.newpage()
grid.draw(gr)

#Realistic example with a custon Unicode character scale.
fake.data <- chain(expand.grid(x=seq(-1,1,length=12),
                               g=0:4),
                   mutate(p = (rbinom(length(x), 50,
                                      plogis(x, g/5-0.5, (5+g)/20))
                               )/50,
                          g = factor(g)))

ggp <- ggplot(fake.data) + aes(x=x, y=p, shape=g) + geom_point()

#custom scale
shape_sequence <- -rev(c(-16, -17, 0x2726L, 0x2605L,
                         0x2736L, 0x2737L, 0x2739L, 0x273AL))
shape_chooser <- function(n) {
  shape_sequence[seq(floor(length(shape_sequence)-n)/2+1, length=n)]
}
custom_shape_scale <-
  list(
    discrete_scale("shape", "manual",
                   palette=shape_chooser, labels=prettyprint)
    )

#edit to set the point font.
gr <- ggplotGrob(ggp + custom_shape_scale)
font <- gpar(fontfamily="MS Gothic", fontsize=14)
gr <- editGtable(gr, "panel", "geom_point\\.points",
                 grep=TRUE, global=TRUE, gp=font)
grid.draw(gr)


#edit the legend to display the font. I give up. This is impossible, or
#at least very hard when gtable does not implkement gTree or gedit
#functions.

keys <- grid.get("guide.box", grep=TRUE)$grobs[[1]]$grobs

lapply(keys, function(x) {
       if ("points" %in% class(x))
         x <- editGrob(x, gp=font)
       x
     }) -> keys

#and then how to stuff them back in???

I'd like to fork this. Where is the chain function defined?