Use an escaped percent sign in TeX and MathJax with pandoc markdown

Question

It's easy to write TeX equations in Markdown documents and convert them to actual typeset equations using pandoc (version 1.18), either in a PDF document (through LaTeX) or an HTML document (through MathJax): surround math in $...$ for inline equations and $$...$$ for block equations.

However, there seems to be a discrepancy between MathJax and TeX syntax with special characters like %. For instance, consider this sample document:

Lorem ipsum dolor sit amet, consectetur adipisicing elit, sed do eiusmod tempor incididunt ut labore et dolore magna aliqua. 

$$\text{\% change} = \frac{x_2 - x_1}{x_1} \times 100$$

Ut enim ad minim veniam, quis nostrud exercitation ullamco laboris nisi ut aliquip ex ea commodo consequat.

Converting this to PDF via LaTeX using the command

pandoc test.md -o test.pdf

correctly produces an unescaped percent sign:

However, converting the same document to HTML with MathJax, using the command

pandoc test.md -s --mathjax -o test.html

incorrectly produces an escaped percent sign:

For now, I've been manually escaping/unescaping percent signs before converting my documents to PDF/HTML, which seems to defeat the purpose of having a master Markdown document that can convert to any format.

What is the correct way to handle escaped percent signs in both TeX and MathJax? Is there a setting in MathJax that allows special characters to be escaped? Do I need to tell LaTeX to accept unescaped percent signs in math mode?

this sounds like a bug in MathJax, are you using the latest version? — mb21
This happens in the current version, 2.7.1: github.com/mathjax/MathJax/releases/tag/2.7.1 — Andrew
The extraneous escape slash appears on the live demo at the main MathJax site too: mathjax.org/#modal-livedemo. This makes me think it's not necessarily a bug, but by design (and on this forum, it sounds like % is not treated a special, escapable character: groups.google.com/d/msg/mathjax-users/Ed1nKT-xtAE/IKvO_NZ9e1QJ) — Andrew
probably has something to do with the \text{} it's in... why not use \percent instead? — mb21
For the record, MathJax does not support macros inside \text{} (with the sole exception of $ to re-enter math mode), see the documentation. — Peter Krautzberger

Danton Noriega Danton Noriega · Accepted Answer · 2017-05-24T03:38:16

(I know this is not tagged under [R] but I know Andrew is an avid R and Rmarkdown user, so I hope this will suffice.)

This is possible using Rmarkdown and knitr. The script below produces the desired outputs when rendered with rmarkdown::render. I also create a gist of the script.

---
title: TEST
output:
    pdf_document:
        latex_engine: xelatex
    html_document:
        fig_caption: true
---

```{r, echo = FALSE}
knitr::opts_chunk$set(
  collapse = TRUE,
  echo = TRUE,
  cache = FALSE,
  comment = "#>",
  fig.path = "fig-",
  fig.pos = "h"
)

# this will check what the output format is going to be
getOutputFormat <- function() {
  knitr::opts_knit$get("rmarkdown.pandoc.to")
}
```


Lorem ipsum dolor sit amet, consectetur adipisicing elit, sed do eiusmod tempor incididunt ut labore et dolore magna aliqua. 

```{r, warning=FALSE, message=FALSE, echo=FALSE, eval=TRUE, results='asis'}
s <- "$$\\text{\\% change} = \\frac{x_2 - x_1}{x_1} \\times 100$$"
if(getOutputFormat() == 'html') s <- gsub('\\\\%', '%', s) # dont escape if html
knitr::asis_output(s)
```

Ut enim ad minim veniam, quis nostrud exercitation ullamco laboris nisi ut aliquip ex ea commodo consequat.

Use an escaped percent sign in TeX and MathJax with pandoc markdown

1 Answers