I need to put Greek letters into facet labels using facet_wrap() in ggplot2. I found a Link describing the same for facet_grid(). I applied this for my data, using the following code:
levels(parameters) <- c(expression(alpha), expression(beta)) p + facet_grid(.~parameters, labeller = label_parsed)
This works great and does exactly what I want. However, I need to use facet_wrap() instead (to get separate y-axes for both paramters, and also to plot even more parameters in different columns and rows). I tried the following:
p + facet_wrap(.~parameters, labeller = label_parsed) , or p + facet_wrap(.~parameters)
but this didn't work because there is no "labeller" function in facet_wrap. How could this be done using grid?
This example should get you started:
library("ggplot2") library("grid") d <- ggplot(iris, aes(Sepal.Length, Sepal.Width)) + geom_point() + facet_wrap(~Species) grob <- ggplotGrob(d) strip_elem <- grid.ls(getGrob(grob, "strip.text.x", grep=TRUE, global=TRUE))$name grob <- grid::editGrob(grob, strip_elem[1], label=expression(alpha[1])) grob <- grid::editGrob(grob, strip_elem[2], label=expression(beta^2)) grob <- grid::editGrob(grob, strip_elem[3], label=expression(hat(gamma))) grid.draw(grob)
Update: this works with ggplot2 version 0.9.3 (although using grid is a fragile way to modify ggplot2 graphics)
grob[["grobs"]][["strip_t.1"]][["children"]][[2]][["label"]] <- expression(alpha[1]) grob[["grobs"]][["strip_t.2"]][["children"]][[2]][["label"]] <- expression(beta^2) grob[["grobs"]][["strip_t.3"]][["children"]][[2]][["label"]] <- expression(hat(gamma)) grid.draw(grob)
