changing expressions to bold face in ggplot2 while preserving its size

Question

I would like to display an expression in a ggplot2 plot axis, where I want to simultaneously change both the size and face for the axis test:

Using ggplot2::element_text, I can change size, but not face.

ggplot(mtcars, aes(cyl, mpg)) + geom_point() +
  scale_x_continuous(
    labels = parse(text = "widehat(mu)=='6'"),
    breaks = 6
  ) +
  ggplot2::theme(axis.text.x = ggplot2::element_text(face = "bold", size = 12))

As suggested here, I can wrap the expression in bold, which partly works (note that only 6 is in bold, and not italic mu) but then the text size doesn't change:

ggplot(mtcars, aes(cyl, mpg)) + geom_point() +
  scale_x_continuous(
    labels = parse(text = "bold(widehat(mu)=='6')"),
    breaks = 6
  ) +
  ggplot2::theme(axis.text.x = ggplot2::element_text(face = "bold", size = 12))

^{Created on 2021-02-12 by the reprex package (v1.0.0)}

Is there any way to do this in ggplot2 itself? Or one will have to use something like ggtext?

Is `.top` in the 2nd `axis.text.x` a typo? Remove it and it works. — Rui Barradas, Feb 12 '21 at 16:52

score 2 · Accepted Answer · answered Feb 12 '21 at 16:56

Here is a way to make the font size vary as requested.
The .top in the second plot's theme seems to be a typo, remove it and the font becomes bigger.
And instead of parse, use expression for plotmath.

library(ggplot2)

ggplot(mtcars, aes(cyl, mpg)) + geom_point() +
  scale_x_continuous(
    labels = expression(bold(widehat(mu) == '6')),
    breaks = 6
  ) +
  theme(axis.text.x = element_text(face = "bold", size = 12))

Here is another one, with the axis label even bigger.

ggplot(mtcars, aes(cyl, mpg)) + geom_point() +
  scale_x_continuous(
    labels = expression(bold(widehat(mu) == '6')),
    breaks = 6
  ) +
  theme(axis.text.x = element_text(face = "bold", size = 24))

changing expressions to bold face in ggplot2 while preserving its size

1 Answers1