Usage
The TeX function takes a LaTeX string, parses it, and
returns the closest plotmath
expression suitable for use in graphics. The return value of
TeX() can be used anywhere a plotmath expression is
accepted, including plot labels, legends, and text for both base
graphics and ggplot2.
Here’s a simple example:
# Use raw strings, no need to escape backslashes.
TeX(r"(\textbf{Euler's identity} is $e^{i\pi} + 1 = 0$.)")In this example, \textbf{} is used to mark a fragment of
text as bold, $ introduces inline math mode,
^{} typesets its contents as superscript, and
\pi typesets the letter \(\pi\).
Starting with R 4.0, it is recommended to use the new raw string
literal syntax (see ?Quotes). The syntax looks like
r"(...)", where ... can contain any character
sequence, including \.
Another option is to escape the backslash character (\)
for LaTeX commands, such that the command will be written as
\\command rather than \command. This will also
work on versions of R older than 4.0:
# Equivalent to the previous code fragment.
# Use regular strings, but escape the backslashes.
TeX("\\textbf{Euler's identity} is $e^{i\\pi} + 1 = 0$.")You can quickly preview what a translated LaTeX string would look
like by using plot:
plot(TeX(r'(A $\LaTeX$ formula: $\frac{2hc^2}{\lambda^5}\frac{1}{e^{\frac{hc}{\lambda k_B T}} - 1}$)'), cex=2, main="")
The following example shows plotting in base graphics:
x <- seq(0, 4, length.out=100)
alpha <- 1:5
plot(x, xlim=c(0, 4), ylim=c(0, 10),
xlab='x', ylab=TeX(r'($\alpha x^\alpha$, where $\alpha \in \{1 \ldots 5\}$)'),
type='n', main=TeX(r'(Using $\LaTeX$ for plotting in base graphics!)', bold=TRUE))
for (a in alpha) {
lines(x, a*x^a, col=a)
}
legend('topleft',
legend=TeX(sprintf(r'($\alpha = %d$)', alpha)),
lwd=1,
col=alpha)
This example shows plotting in ggplot2:
x <- seq(0, 4, length.out=100)
alpha <- 1:5
data <- map_df(alpha, ~ tibble(v=.*x^., x=x, alpha=.))
p <- ggplot(data, aes(x=x, y=v, color=as.factor(alpha))) +
geom_line() +
ylab(TeX(r'($\alpha x^\alpha$, where $\alpha \in 1\ldots 5$)')) +
ggtitle(TeX(r'(Using $\LaTeX$ for plotting in ggplot2. I $\heartsuit$ ggplot!)')) +
coord_cartesian(ylim=c(-1, 10)) +
guides(color=guide_legend(title=NULL)) +
scale_color_discrete(labels=lapply(sprintf(r'($\alpha = %d$)', alpha), TeX))
# Note that ggplot2 legend labels must be lists of expressions, not vectors of expressions
print(p)
Here are a few examples of what you can do with latex2exp:
latex2exp_examples(cex=0.9)