Getting LaTeX into R Plots

Data visualization is a cornerstone of exploratory data analysis, enabling analysts to effectively glean insights and communicate findings. Mathematical notation often accompanies visualizations in scientific and technical fields, elucidating complex relationships and phenomena.

Understanding LaTeX in R

LaTeX, pronounced "lay-tech" or "lah-tech," is a typesetting system widely used for producing scientific and technical documents. It excels at formatting complex mathematical expressions, equations, and symbols with unparalleled precision and aesthetic appeal. LaTeX documents in the R Programming Language are created using plain text files containing markup commands that specify the structure and formatting of the document.

Bringing Math to Plots in R

In the realm of data visualization, R reigns supreme, offering a diverse array of packages such as ggplot2, plotly, and lattice for creating stunning visualizations. While these packages excel at rendering graphical representations of data, they often lack native support for rendering mathematical notation. Enter LaTeX—a natural companion to R plots, enabling analysts to seamlessly embed mathematical expressions and symbols into their visualizations.

1. Using expression for Basic Mathematical Annotation

R's base graphics system supports a limited set of mathematical annotations using the expression function. This method is straightforward for simple mathematical expressions.

plot(1:10, main=expression(sqrt(x) == y))

Output:

In this example, expression(sqrt(x) == y) generates the LaTeX-like notation for the plot title, representing the square root function.

2. Enhanced Mathematical Annotation with latex2exp

The latex2exp package allows more extensive use of LaTeX in R plots by converting LaTeX strings into expressions that R can render. This package is particularly useful for those familiar with LaTeX syntax.

library(latex2exp)

plot(1:10, main=TeX('$e^{i\\pi} + 1 = 0$'))

Output:

Here, TeX('$e^{i\\pi} + 1 = 0$') converts the LaTeX string into a format that R can interpret and render in the plot title, showcasing Euler's identity.

3. Using ggplot2 with latex2exp

The ggplot2 package, a popular system for creating complex and customizable graphics, can also integrate with latex2exp.

library(ggplot2)
library(latex2exp)

ggplot(data.frame(x = 1:10, y = (1:10)^2), aes(x, y)) +
  geom_point() +
  ggtitle(TeX('$y = x^2$'))

Output:

In this ggplot2 example, the title of the plot is set using a LaTeX string representing the quadratic function y=x2y = x^2y=x2.

4. Customizing LaTeX Rendering with plotmath

While latex2exp and tikzDevice provide robust solutions, R's base plotmath system also offers a range of customization options for mathematical annotation.

plot(1:10, main=expression(infinity == limit(x %->% infinity, (1 + frac(1, x))^x)))

Output:

In this case, expression(infinity == limit(x %->% infinity, (1 + frac(1, x))^x)) uses the plotmath system to represent the limit defining Euler's number eee.

Conclusion

Incorporating LaTeX into R plots enhances the clarity and professionalism of your visualizations, particularly when dealing with complex mathematical expressions. Whether using base R graphics, ggplot2, grid, or exporting to PDF, various tools and packages like latex2exp and tikzDevice facilitate this process. By leveraging these techniques, you can create precise and high-quality plots suitable for academic publications and professional presentations.