epoxy makes glue easy to use in R Markdown documents.
epoxy is in a proof-of-concept stage right now. I’m still
experimenting, so the API may will change. I’d love to hear your
thoughts, feel free to open
issues.
You can install the proof-of-concept version of epoxy with remotes.
# install.packages("remotes")
remotes::install_github("gadenbuie/epoxy")
library(epoxy)
Loading epoxy adds a new chunk type called glue
.
You can write regular markdown in the glue
chunk, wrapping any R
expressions in {...}
, just like in glue::glue()
.
```{glue}
The average speed of the cars was **{mean(cars$speed)} mph.**
But on average the distance travelled was only _{mean(cars$dist)}_.
```
The average speed of the cars was 15.4 mph. But on average the distance travelled was only 42.98 ft.
All of the arguments of glue::glue()
are available as chunk options,
so you can configure the .open
and .close
characters, e.g. {{
instead of {
, among other options.
With an amazing stroke of luck, RStudio autocompletion works inside
glue
chunks!
You can use the expoxy_style_wrap()
with the .transformer
chunk
option to wrap the evaluated R expression in formating or templating
text. Or you can use the pre-set epoxy_style_bold()
,
epoxy_style_italic()
, or epoxy_style_code()
style transformers.
```{glue, .transformer = epoxy_style_bold()}
All cars stopped between {min(cars$dist)} and {max(cars$dist)} feet
from a starting speed of {min(cars$speed)}---{max(cars$speed)}
```
All cars stopped between 2 and 120 feet from a starting speed of 4—120 mph.
Unlike inline R code, the glue
chunks are vectorized. This can be
something to watch out for or it can be an advantage:
```{glue}
{1:4}. "{letters[1:4]}" is for {c("apple", "banana", "coconut", "donut")}
```
- “a” is for apple
- “b” is for banana
- “c” is for coconut
- “d” is for donut
You can collapse fields automatically using the epoxy_style_collapse()
transformer. You can then choose how vectors are collapsed by adding
*
, &
or |
to the end of the expression.
*
collapses with commas, e.g.{letters[1:3]*}
.&
collapses with commas and adds" and "
between the last two items|
collapses with commas and adds" or "
between the last two items.
```{glue, .transformer = epoxy_style_collapse()}
- The first three letters are {letters[1:3]*}.
- When capitalized, they are {LETTERS[1:3]&}.
- They're indexed by {1:3|}.
```
- The first three letters are a, b, c.
- When capitalized, they are A, B and C.
- They’re indexed by 1, 2 or 3.
You can change the separator between entries and between the last entry
using the sep
, last
and the _and
and _or
specific arguments of
the epoxy_style_collapse()
function.
It’s also possible to create a reusable template. Use the ref.label
chunk option to reuse a template using the values in the data
chunk
option, which can be a list or data frame.
mpg <- data.frame(
manufacturer = c("Chevrolet", "Dodge", "Ford"),
model = c("Malibu", "Caravan", "Expedition"),
cty = c(19, 7, 11),
hwy = c(27, 24, 17)
)
```{glue car-name, eval=FALSE}
- A {manufacturer} {model} gets {cty} city and {hwy} highway miles per gallon.
```
```{glue ref.label="car-name", data = mpg}
```
- A Chevrolet Malibu gets 19 city and 27 highway miles per gallon.
- A Dodge Caravan gets 7 city and 24 highway miles per gallon.
- A Ford Expedition gets 11 city and 17 highway miles per gallon.
Sometimes the glue
engine doesn’t quite deliver the template power you
need. In these cases, you can use the whisker
engine instead.
```{r}
contestant <- list(name = "R User", value = 1000, taxed = 600, in_ca = TRUE)
```
```{whisker data = contestant, echo=FALSE}
Hello {{name}}:
You have just won ${{value}}!
{{#in_ca}}
Well, ${{taxed}}, after taxes.
{{/in_ca}}
```
contestant <- list(name = "R User", value = 1000, taxed = 600, in_ca = TRUE)
Hello R User: You have just won $1000! Well, $600, after taxes.
Use the glue_html
block to glue R and HTML together. The output is
raw HTML. By default,
expressions in these types of blocks are wrapped in {{
and }}
, like
whisker templates above.
<ul>
```{glue_html, data = mpg}
<li><strong>{{manufacturer}}</strong> <em>{{model}}</em></li>
```
</ul>
- Chevrolet Malibu
- Dodge Caravan
- Ford Expedition
Similarly, you can also use glue_latex
blocks to glue R and LaTeX
together. By default, expressions in these types of blocks are wrapped
in <
and >
.
\begin{itemize}
```{glue_latex, data = mpg}
\item \textbf{<manufacturer>} \textit{<model>} gets <cty> city and <hwy> highway miles per gallon.
```
\end{itemize}
In R Markdown knitting into a LaTeX output, this renders as:
\begin{itemize}
\item \textbf{Chevrolet} \textit{Malibu} gets 19 city and 27 highway miles per gallon.
\item \textbf{Dodge} \textit{Caravan} gets 7 city and 24 highway miles per gallon.
\item \textbf{Ford} \textit{Expedition} gets 11 city and 17 highway miles per gallon.
\end{itemize}