# Based on code from Simon Potter's Masters thesis
# (~/Files/Teaching/Simon2012/thesis-notes/thesis/tex/referenced-content.Rnw)

library(gridSVG)

plotdat <- aggregate(hp ~ gear + vs, data = mtcars, mean)
plotdat$gear <- factor(plotdat$gear)
plotdat$vs <- factor(plotdat$vs)
# Let's have a look at the data
plotdat
# Plot a barchart
library(lattice)

# From trellis.par.get("superpose.polygon")
fills <- c("#CCFFFF", "#FFCCFF")
val0pat <- pattern(gTree(children=gList(
                             rectGrob(gp=gpar(col=NA, fill=fills[1])),
                             linesGrob(gp=gpar(col="black")))),
                   width = unit(2, "mm"), height = unit(2, "mm"),
                   dev.width = 1, dev.height = 1)
val1pat <- pattern(gTree(children=gList(
                             rectGrob(gp=gpar(col=NA, fill=fills[2])),
                             linesGrob(0:1, 1:0, gp=gpar(col="black")))),
                   width = unit(2, "mm"), height = unit(2, "mm"),
                   dev.width = 1, dev.height = 1)
barchart(hp ~ gear, groups = vs, data = plotdat,
         xlab = "Number of Gears", ylab = "Mean Horsepower",
         auto.key = list(space = "right"), horizontal = FALSE)
# Registering patterns
registerPatternFill("val0pat", val0pat)
registerPatternFill("val1pat", val1pat)
# Applying pattern fills
barNames <- paste0("plot_01.barchart.x.", 1:3,
                   ".rect.panel.1.1")
for (i in 1:3) {
    grid.patternFill(barNames[i],
                     label = c("val0pat", "val1pat"),
                     group = FALSE)
}
# Applying legend pattern fills
legendNames <- paste0("plot_01.key.rect.2.", 1:2)
grid.patternFill(legendNames[1], label = "val0pat",
                 group = FALSE)
grid.patternFill(legendNames[2], label = "val1pat",
                 group = FALSE)

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