p <- qplot(mpg, wt, data=mtcars, colour=factor(cyl))
p + scale_colour_grey()
p + scale_colour_grey(end = 0)
# You may want to turn off the pale grey background with this scale
p + scale_colour_grey() + theme_bw()
# Colour of missing values is controlled with na.value:
miss <- factor(sample(c(NA, 1:5), nrow(mtcars), rep = TRUE))
qplot(mpg, wt, data = mtcars, colour = miss) + scale_colour_grey()
qplot(mpg, wt, data = mtcars, colour = miss) +
scale_colour_grey(na.value = "green")
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