# Command-line program to update R Markdown code to use `$latex` delimter

**UPDATE (13th June 2012):** RStudio now supports a range of mathjax delimtiers including single dollar signs and double dollar signs without `latex`

.

In 0.96 RStudio changed its Mathjax syntax from `$<equation>$`

to `$latex <equation>$`

for inline equations and from `$$<equation>$$`

to `$$latex <equation>$$`

for displayed equations.

Thus, in summary:

The revised syntax adds a

`latex`

qualifier to the $ or $$ equation begin delimiter.

I have some existing scripts that use the original `$`

delimiter and I would like to update them to use the new `$latex`

delimiter.

I was thinking that sed or awk might be suitable.

Also dollars that appear in r code blocks like this should not be altered.

```{r ...} x <- Data$asdf ```

Question

- What would be a good simple command-line program perhaps using sed or awk to update my R Markdown code to use the newer mathjax delimiter in R Studio?

Working example 1

Original text:

$y = a + b x$ is the formula. This is some text, and here is a displayed formula $$y = a+ bx\\ x = 23$$ ```{r random_block} y <- Data$asdf ``` and some more text $$y = a+ bx\\ x = 23$$

after transformation becomes

$latex y = a + b x$ is the formula. This is some text, and here is a displayed formula $$latex y = a+ bx\\ x = 23$$ ```{r random_block} y <- Data$asdf ``` and some more text $$latex y = a+ bx\\ x = 23$$

Working example 2

`r opts_chunk$set(cache=TRUE)` <!-- some comment --> Some text <!-- more --> Observed data are $y_i$ where $i=1, \ldots, I$. $$y_i \sim N(\mu, \sigma^2)$$ Some text $\sigma^2$ blah blah $\tau$. $$\tau = \frac{1}{\sigma^2}$$ blah blah $\mu$ and $\tau$ $$\mu \sim N(0, 0.001)$$ $$\tau \sim \Gamma(0.001, 0.001)$$

should become

`r opts_chunk$set(cache=TRUE)` <!-- some comment --> Some text <!-- more --> Observed data are $latex y_i$ where $latex i=1, \ldots, I$. $$latex y_i \sim N(\mu, \sigma^2)$$ Some text $latex \sigma^2$ blah blah $latex \tau$. $$latex \tau = \frac{1}{\sigma^2}$$ blah blah $latex \mu$ and $latex \tau$ $$latex \mu \sim N(0, 0.001)$$ $$latex \tau \sim \Gamma(0.001, 0.001)$$