Using PrismJS with {xaringan}

# Using PrismJS with {`xaringan`} via `prismr`

]

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---

# PrismJS works with `fansi` knit hooks

```r
library(tidyverse)
```

<PRE class="fansi fansi-message"><CODE>## -- Attaching packages --------------------------------------- tidyverse 1.3.1 --
</CODE></PRE><PRE class="fansi fansi-message"><CODE>## v ggplot2 3.3.6 v purrr 0.3.4
## v tibble 3.1.6 v dplyr 1.0.9
## v tidyr 1.2.0 v stringr 1.4.0
## v readr 2.1.2 v forcats 0.5.1
</CODE></PRE><PRE class="fansi fansi-message"><CODE>## -- Conflicts ------------------------------------------ tidyverse_conflicts() --
## x dplyr::filter() masks stats::filter()
## x dplyr::lag() masks stats::lag()
</CODE></PRE>

---

# PrismJS works with `fansi` knit hooks

```r
tidyverse_logo()
```

---

# Example code and output

```r
new_penguins <- palmerpenguins::penguins %>%
 drop_na() %>%
 mutate(bill_length_mean1 = mean(bill_length_mm)) %>%
 group_by(species, island) %>%
 mutate(bill_length_mean2 = mean(bill_length_mm)) %>%
 ungroup() %>%
 select(species, island, contains("bill_length"))

new_penguins
```

<PRE class="fansi fansi-output"><CODE>## # A tibble: 333 x 5
## species island bill_length_mm bill_length_mean1 bill_length_mean2
## &lt;fct&gt; &lt;fct&gt; &lt;dbl&gt; &lt;dbl&gt; &lt;dbl&gt;
## 1 Adelie Torgersen 39.1 44.0 39.0
## 2 Adelie Torgersen 39.5 44.0 39.0
## 3 Adelie Torgersen 40.3 44.0 39.0
## 4 Adelie Torgersen 36.7 44.0 39.0
## 5 Adelie Torgersen 39.3 44.0 39.0
## 6 Adelie Torgersen 38.9 44.0 39.0
## 7 Adelie Torgersen 39.2 44.0 39.0
## 8 Adelie Torgersen 41.1 44.0 39.0
## 9 Adelie Torgersen 38.6 44.0 39.0
## 10 Adelie Torgersen 34.6 44.0 39.0
## # ... with 323 more rows
</CODE></PRE>

---

# Highlighting code inline without defining a slide class

You can also highlight inline code using the usual dot-classes, with the class being "language-r".

So I thought I'd use .language-r[`dplyr::group_by()`] followed by .language-r[`dplyr::mutate()`].
Of course, afterward I would also .language-r[`dplyr::ungroup()`].

You can also use the class "language-none" to disable highlighting of inline code.

So I thought I'd use .language-none[`dplyr::group_by()`] followed by .language-none[`dplyr::mutate()`].
Of course, afterward I would also .language-none[`dplyr::ungroup()`].

---

# You may be interested in using the `layout` feature

Recall that you can define slide classes for all subsequent slides using `layout`. As usual, you
can also combine classes together.

```
class: center, inverse, language-r
layout: true
```

Read more about slide layouts
[<svg aria-hidden="true" role="img" viewBox="0 0 512 512" style="height:1em;width:1em;vertical-align:-0.125em;margin-left:auto;margin-right:auto;font-size:inherit;fill:currentColor;overflow:visible;position:relative;"><path d="M432,320H400a16,16,0,0,0-16,16V448H64V128H208a16,16,0,0,0,16-16V80a16,16,0,0,0-16-16H48A48,48,0,0,0,0,112V464a48,48,0,0,0,48,48H400a48,48,0,0,0,48-48V336A16,16,0,0,0,432,320ZM488,0h-128c-21.37,0-32.05,25.91-17,41l35.73,35.73L135,320.37a24,24,0,0,0,0,34L157.67,377a24,24,0,0,0,34,0L435.28,133.32,471,169c15,15,41,4.5,41-17V24A24,24,0,0,0,488,0Z"/></svg>](https://github.com/yihui/xaringan/wiki/Slide-layouts).

---

# Limitations

One known limitation is that adding comments will highlight the remainder of the chunk as a comment
[<svg aria-hidden="true" role="img" viewBox="0 0 512 512" style="height:1em;width:1em;vertical-align:-0.125em;margin-left:auto;margin-right:auto;font-size:inherit;fill:currentColor;overflow:visible;position:relative;"><path d="M432,320H400a16,16,0,0,0-16,16V448H64V128H208a16,16,0,0,0,16-16V80a16,16,0,0,0-16-16H48A48,48,0,0,0,0,112V464a48,48,0,0,0,48,48H400a48,48,0,0,0,48-48V336A16,16,0,0,0,432,320ZM488,0h-128c-21.37,0-32.05,25.91-17,41l35.73,35.73L135,320.37a24,24,0,0,0,0,34L157.67,377a24,24,0,0,0,34,0L435.28,133.32,471,169c15,15,41,4.5,41-17V24A24,24,0,0,0,488,0Z"/></svg>](https://github.com/adamoshen/prismr/issues/2).

```r
1 + 2

# Everything past this point will be highlighted as a comment
mean(c(1, 4, 5, 6))
data(starwars, package="dplyr")
```

Solutions:

- Only include comments on the last line, or adjacent to the last line of code
- Don't include comments in your code chunk
- Start a new code chunk after commenting
- Use plain text on the slide to explain your code
- Line highlighting still works though (see next slide)

---

# This is something complicated

```r
ggplot(
* mpg,
  
  aes(x = displ, y = hwy, colour = class)
) +
  geom_point()
```

]

Construct a plot using the .language-none[`mpg`] data set.

]

```r
ggplot(
  mpg,
  
* aes(x = displ, y = hwy, colour = class)
) +
  geom_point()
```

]

The x-axis will represent engine displacement.

The y-axis will represent highway miles per gallon.

Geoms will be coloured by type of vehicle

]

```r
ggplot(
  mpg,
  
  aes(x = displ, y = hwy, colour = class)
) +
* geom_point()
```

]

Draw points on the canvas.

]