Installation

Install this package from CRAN:

install.packages('latex2exp')

You can also install from GitHub using devtools:

devtools::install_github('stefano-meschiari/latex2exp')

Usage

library(latex2exp)

The TeX function takes a LaTeX string and returns a plotmath expression suitable for use in plotting, e.g.,

TeX('$\\alpha^\\beta$')

(note it is always necessary to escape the backslash within a string, hence the double backslash).

The return value of TeX() can be used anywhere a plotmath expression is accepted, including plot labels, legends, and text.

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('$\\alpha  x^\\alpha$, where $\\alpha \\in 1\\ldots 5$'), 
     type='n', main=TeX('Using $\\LaTeX$ for plotting in base graphics!'))

invisible(sapply(alpha, function(a) lines(x, a*x^a, col=a)))

legend('topleft', legend=TeX(sprintf("$\\alpha = %d$", alpha)), 
       lwd=1, col=alpha)

This example shows plotting in ggplot2:

library(plyr)
library(ggplot2)
x <- seq(0, 4, length.out=100)
alpha <- 1:5
data <- mdply(alpha, function(a, x) data.frame(v=a*x^a, x=x), x)

p <- ggplot(data, aes(x=x, y=v, color=X1)) +
    geom_line() + 
    ylab(TeX('$\\alpha  x^\\alpha$, where $\\alpha \\in 1\\ldots 5$')) +
    ggtitle(TeX('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('$\\alpha = %d$', alpha), TeX)) 
    # Note that ggplot2 legend labels must be lists of expressions, not vectors of expressions

print(p)

You can quickly test out what a translated LaTeX string would look like by using plot:

plot(TeX("A $\\LaTeX$ formula: $\\frac{2hc^2}{\\lambda^5} \\, 
               \\frac{1}{e^{\\frac{hc}{\\lambda k_B T}} - 1}$"), cex=2)

Syntax

Use

TeX('latexString')

to build a plotmath expression, ready for use in plots. If the parser cannot build a correct plotmath expression, it will stop() and show the invalid plotmath expression built.

TeX('latexString', output=c('expression', 'character', 'ast'))

If the output option is equal to character, it will return the string representation of the expression (which could be converted into an expression using parse(text=)).

If the output option is equal to ast, it will return the tree built by the parser (this is only useful for debugging).

latex2exp_examples()

will show a demo of the supported LaTeX syntax.

latex2exp_supported(plot=FALSE)

returns a list of supported LaTeX. If plot=TRUE, a table of symbols will be plotted.

“Supported” LaTeX

Formulas should go between dollar characters ($).

Only a subset of LaTeX is supported, and not 100% correctly. Greek symbols (\alpha, \beta, etc.) and the usual operators (+, -, etc.) are supported.

In addition, the following should be supported:

latex2exp_supported(plot=TRUE)

Their rendering depends on R’s interpretation of the plotmath expression.

A few examples:

latex2exp_examples()

## [1] TRUE

Changes