Getting LaTeX into R Plots

I would like to add LaTeX typesetting to elements of plots in R (e.g: the title, axis labels, annotations, etc.) using either the combination of base/lattice or with ggplot2.

Questions:

• Is there a way to get LaTeX into plots using these packages, and if so, how is it done?
• If not, are there additional packages needed to accomplish this.

For example, in Python matplotlib compiles LaTeX via the text.usetex packages as discussed here: http://www.scipy.org/Cookbook/Matplotlib/UsingTex

Is there a similar process by which such plots can be generated in R?

[The CRAN package latex2exp][1] contains a TeX function that translate LaTeX formulas to R's plotmath expressions. You can use it anywhere you could enter mathematical annotations, such as axis labels, legend labels, and general text.

For example:

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)

produces [this plot][2].

[1]: https://github.com/stefano-meschiari/latex2exp "latex2exp" [2]: https://www.stefanom.io/latex2exp/reference/figures/README-base-plot-1.png

Here's an example using ggplot2:

q <- qplot(cty, hwy, data = mpg, colour = displ)
q + xlab(expression(beta +frac(miles, gallon)))

As stolen from here, the following command correctly uses LaTeX to draw the title:

plot(1, main=expression(beta[1]))

See ?plotmath for more details.

You can generate tikz code from R: http://r-forge.r-project.org/projects/tikzdevice/

Here's something from my own Lab Reports.

• tickzDevice exports tikz images for LaTeX

• Note, that in certain cases "\\" becomes "\" and "$" becomes "$\" as in the following R code: "$z\\frac{a}{b}$" -> "$\z\frac{a}{b}$\"

• Also xtable exports tables to latex code

The code:

library(reshape2)
library(plyr)
library(ggplot2)
library(systemfit)
library(xtable)
require(graphics)
require(tikzDevice)

setwd("~/DataFolder/")
Lab5p9 <- read.csv (file="~/DataFolder/Lab5part9.csv", comment.char="#")

AR <- subset(Lab5p9,Region == "Forward.Active")

# make sure the data names aren't already in latex format, it interferes with the ggplot ~  # tikzDecice combo
colnames(AR) <- c("$V_{BB}[V]$", "$V_{RB}[V]$" ,  "$V_{RC}[V]$" , "$I_B[\\mu A]$" , "IC" , "$V_{BE}[V]$" , "$V_{CE}[V]$" , "beta" , "$I_E[mA]$")

# make sure the working directory is where you want your tikz file to go
setwd("~/TexImageFolder/")

# export plot as a .tex file in the tikz format
tikz('betaplot.tex', width = 6,height = 3.5,pointsize = 12) #define plot name size and font size

#define plot margin widths
par(mar=c(3,5,3,5))	# The syntax is mar=c(bottom, left, top, right).

ggplot(AR, aes(x=IC, y=beta)) +                                # define data set 
	geom_point(colour="#000000",size=1.5) +                # use points
	geom_smooth(method=loess,span=2) +                     # use smooth
	theme_bw() +  					# no grey background
	xlab("$I_C[mA]$") + 				# x axis label in latex format
	ylab ("$\\beta$") + 				# y axis label in latex format
	theme(axis.title.y=element_text(angle=0)) +	# rotate y axis label
	theme(axis.title.x=element_text(vjust=-0.5)) +  # adjust x axis label down
	theme(axis.title.y=element_text(hjust=-0.5)) +  # adjust y axis lable left
	theme(panel.grid.major=element_line(colour="grey80", size=0.5)) +# major grid color
	theme(panel.grid.minor=element_line(colour="grey95", size=0.4)) +# minor grid color 
	scale_x_continuous(minor_breaks=seq(0,9.5,by=0.5)) +# adjust x minor grid spacing
	scale_y_continuous(minor_breaks=seq(170,185,by=0.5)) + # adjust y minor grid spacing
	theme(panel.border=element_rect(colour="black",size=.75))# border color and size

dev.off() # export file and exit tikzDevice function

Here's a cool function that lets you use the plotmath functionality, but with the expressions stored as objects of the character mode. This lets you manipulate them programmatically using paste or regular expression functions. I don't use ggplot, but it should work there as well:

    express <- function(char.expressions){
       return(parse(text=paste(char.expressions,collapse=";")))
    }
    par(mar=c(6,6,1,1))
    plot(0,0,xlim=sym(),ylim=sym(),xaxt="n",yaxt="n",mgp=c(4,0.2,0),
       xlab="axis(1,(-9:9)/10,tick.labels,las=2,cex.axis=0.8)",
       ylab="axis(2,(-9:9)/10,express(tick.labels),las=1,cex.axis=0.8)")
    tick.labels <- paste("x >=",(-9:9)/10)
    # this is what you get if you just use tick.labels the regular way:
    axis(1,(-9:9)/10,tick.labels,las=2,cex.axis=0.8)
    # but if you express() them... voila!
    axis(2,(-9:9)/10,express(tick.labels),las=1,cex.axis=0.8)

I did this a few years ago by outputting to a .fig format instead of directly to a .pdf; you write the titles including the latex code and use fig2ps or fig2pdf to create the final graphic file. The setup I had to do this broke with R 2.5; if I had to do it again I'd look into tikz instead, but am including this here anyway as another potential option.

My notes on how I did it using Sweave are here: http://www.stat.umn.edu/~arendahl/computing

I just have a workaround. One may first generate an eps file, then convert it back to pgf using the tool eps2pgf. See http://www.texample.net/tikz/examples/eps2pgf/

h <- rnorm(mean = 5, sd = 1, n = 1000) hist(h, main = expression(paste("Sampled values, ", mu, "=5, ", sigma, "=1")))

Taken from a very help article here https://stats.idre.ucla.edu/r/codefragments/greek_letters/