facet label font size [duplicate]
Solution 1:
This should get you started:
R> qplot(hwy, cty, data = mpg) +
facet_grid(. ~ manufacturer) +
theme(strip.text.x = element_text(size = 8, colour = "orange", angle = 90))
See also this question: How can I manipulate the strip text of facet plots in ggplot2?