rggplot2mathplot

Maths font for letter (e.g. x) in R ggplot legends

I want to have a plot with a legend displaying x_0, with a font that looks "mathematical" for x (I don't know how to say that otherwise), like 𝒙_0.

When I use expression(x[0]), this is what I get :

enter image description here

How can I get a font for x that doesn't look like a basic cross like this ?

Solution

  • My first idea on this was to use unicode, but this requires the user to either know them by heart or search them on the internet. So I thought why not use extrafont to load in a Calligraphic font for math text and a normal font like Calibri for normal non-math Text for italic and then mix them both together in expression('x'[italic('0')])

    library(ggplot2)
library(extrafont)
library(showtext)

#system.fonts <- systemfonts::system_fonts() # look into your system's fonts

font_add("LucidaCalligraphy-Italic", "LCALLIG.TTF", italic = "calibri.ttf") # LaTeX uses Calligraphic for MathCal

showtext_auto()

ggplot(data.frame(
  x = c(1,2),
  y = c(1,2),
  group = c("A", "B")
), aes(x = x, y = y, color = group)) +
  geom_point() +
  labs(color = expression('x'[italic('0')])) + 
  theme(text = element_text(size = 22),
        legend.title = element_text(family = "LucidaCalligraphy-Italic"))

    giving

    out