Make arbitrary glyphs with R graphic devices

Loon's primitive glyph types are limited in terms of compound shapes. With this function you can create each point glyph as a png and re-import it as a tk img object to be used as point glyphs in loon. See the examples.

l_make_glyphs(data, draw_fun, width = 50, height = 50, ...)

Arguments

data	list where each element contains a data object used for the draw_fun
draw_fun	function that draws a glyph using R base graphics or the grid (including ggplot2 and lattice) engine
width	width of each glyph in pixel
height	height of each glyph in pixel
...	additional arguments passed on to the png function

Value

vector with tk img object references

Examples

if (FALSE) {
if (requireNamespace("maps", quietly = TRUE)) {
  data(minority)
  p <- l_plot(minority$long, minority$lat)

  canada <- maps::map("world",  "Canada", fill=TRUE, plot=FALSE)
  l_map <- l_layer(p, canada, asSingleLayer=TRUE)
  l_scaleto_world(p)

  img <- l_make_glyphs(lapply(1:nrow(minority), function(i)minority[i,]), function(m) {
      par(mar=c(1,1,1,1)*.5)
      mat <- as.matrix(m[1,1:10]/max(m[1:10]))
      barplot(height = mat,
              beside = FALSE,
              ylim = c(0,1),
              axes= FALSE,
              axisnames=FALSE)
  }, width=120, height=120)

  l_imageviewer(img)

  g <- l_glyph_add_image(p, img, "barplot")
  p['glyph'] <- g

}

## with grid
if (requireNamespace("grid", quietly = TRUE)) {

  li <- l_make_glyphs(runif(6), function(x) {
      if(any(x>1 | x<0))
          stop("out of range")
      grid::pushViewport(grid::plotViewport(grid::unit(c(1,1,1,1)*0, "points")))
      grid::grid.rect(gp=grid::gpar(fill=NA))
      grid::grid.rect(0, 0, height = grid::unit(x, "npc"), just = c("left", "bottom"),
                gp=grid::gpar(col=NA, fill="steelblue"))
  })

  l_imageviewer(li)

  p <- l_plot(1:6)
  g <- l_glyph_add_image(p, li, "bars")
  p['glyph'] <- g
}

}