How to apply cross-hatching to a polygon using the grid graphical system?

Question

Several functions in R\'s base graphical system, including rect() and polygon(), support cross-hatching via their angle= and den

Answer 1

Here's an example with gridSVG adapted from Paul Murrell's presentation

library(gridSVG)
library(grid)
x = c(0, 0.5, 1, 0.5)
y = c(0.5, 1, 0.5, 0)
grid.newpage()
grid.polygon(x,y, name="goodshape")

pat <- pattern(linesGrob(gp=gpar(col="black",lwd=3)),
  width = unit(5, "mm"), height = unit(5, "mm"),
  dev.width = 1, dev.height = 1)

# Registering pattern
registerPatternFill("pat", pat)
# Applying pattern fill
grid.patternFill("goodshape", label = "pat")

grid.export("test-pattern.svg")

more complex grobs are allowed as well, since svg takes care of the clipping.