How to add superscripts to facet labels

Question

I am trying to plot three variables and want the units in the axes labels but can't find a way to label them properly in facets with the superscripts.

I've tried as_labeller, label_bquote, expression/paste and changing the original data.

p <- ggplot(data = LST, aes(x = Date, y = Measurements)) + 
geom_point((aes(color = parameter)))

p + facet_grid(parameter ~ ., scales = "free_y", 
switch="y",labeller=as_labeller(DO~(mg~L^{-1}), Temperature~(°C), Light~ 
(µmol~m^{-2}~s^{-1}))) + 
            theme_bw()+ theme(strip.background = element_blank(), 
legend.title = element_blank(), strip.placement = "outside", 
panel.grid.minor = element_blank()) + 
          scale_x_datetime()+ ylab(NULL) +ggtitle("Spring 2018") + 
scale_colour_manual(values=c('royalblue1', 'springgreen4', 'darkblue')) +
          theme(legend.position="none")+ 
theme(strip.text=element_text(size=10))

Everything I try either labels all facets the same or doesn't place the superscripts. I'm pretty new at ggplot2 so am unsure if what I'm trying will help.

Answer 1

You want labeller = label_parsed. Here's a simple example

mt = mtcars

mt$facets = factor(mt$cyl, labels = c(
    "DO~(mg~L^{-1})", 
    "Temperature~('°C')", 
    "Light~(µmol~m^{-2}~s^{-1})"))

ggplot(mt, aes(mpg,cyl)) +
  geom_point() +
  facet_grid(~facets, labeller = label_parsed)