Tutorial part 2: Writing a post

The slum provides a simple Hugo theme intended primarily to be used in conjunction with the blogdown package, so posts take the form of R Markdown documents rather than plain markdown. I’m fairly certain that the theme supports plain markdown, but given that the appeal of blogdown lies in integrating R Markdown with the Hugo blogging system I’ll jump straight to it.

1. The YAML header

Like any R Markdown document, a post begins with the YAML header. For this post, the header looks like this:

---
title: "Tutorial part 2: Writing a post"
author: "Danielle Navarro"
date: "2019-04-13"
slug: writing-a-post
tags: ["slum", "blogdown", "slumstyle"]
summary: "Like any blogdown post, a slumdown post is written in R Markdown, and uses a few custom fields in the YAML field. This tutorial provides an illustration of how different kinds of content are displayed."
header:
  caption: "A blank ggplot"
  image: 'header/theme_dark.png'
---

Note that I specified the post summary manually. If you don’t do it yourself, the template will set one for you but it won’t look very nice.

2. R chunks

As usual, R chunks can be inserted:

library(tidyverse)
library(slumdown)

Code that produces console output renders like this:

glimpse(mpg)
## Rows: 234
## Columns: 11
## $ manufacturer <chr> "audi", "audi", "audi", "audi", "audi", "audi", "audi", …
## $ model        <chr> "a4", "a4", "a4", "a4", "a4", "a4", "a4", "a4 quattro", …
## $ displ        <dbl> 1.8, 1.8, 2.0, 2.0, 2.8, 2.8, 3.1, 1.8, 1.8, 2.0, 2.0, 2…
## $ year         <int> 1999, 1999, 2008, 2008, 1999, 1999, 2008, 1999, 1999, 20…
## $ cyl          <int> 4, 4, 4, 4, 6, 6, 6, 4, 4, 4, 4, 6, 6, 6, 6, 6, 6, 8, 8,…
## $ trans        <chr> "auto(l5)", "manual(m5)", "manual(m6)", "auto(av)", "aut…
## $ drv          <chr> "f", "f", "f", "f", "f", "f", "f", "4", "4", "4", "4", "…
## $ cty          <int> 18, 21, 20, 21, 16, 18, 18, 18, 16, 20, 19, 15, 17, 17, …
## $ hwy          <int> 29, 29, 31, 30, 26, 26, 27, 26, 25, 28, 27, 25, 25, 25, …
## $ fl           <chr> "p", "p", "p", "p", "p", "p", "p", "p", "p", "p", "p", "…
## $ class        <chr> "compact", "compact", "compact", "compact", "compact", "…

3. Theme-consistent plots

Because slum was written with the blogdown user in mind, the accompanying slumstyle package allows a modest amount of integration between the R side to the blog and the Hugo side. At the moment this is limited to providing a theme_slum() function for styling ggplot2 output. For instance, this site uses the “dark” colour theme, as specified by the following line in the config.toml file:

colourScheme = "css/colour_dark.css"

To create ggplot output that mirrors this theme, make sure that the slumstyle package is loaded and then it is as simple as specifying theme_slum(dark), as shown in Figure 1 below:

ggplot(mpg, aes(displ, hwy)) + 
  geom_point() + theme_slum("dark")

Figure 1: Here is a plot

By default the slum theme provides this “dark” colour scheme, but there is also a “light” scheme and a “kunoichi” scheme. I’ll talk more about colour schemes in the next post.

4. LaTeX

Inline LaTeX expressions look like this:

$${\sqrt {n}}\left(\left({\frac {1}{n}}\sum _{i=1}^{n}X_{i}\right)-\mu \right)\ {\xrightarrow {d}}\ N\left(0,\sigma ^{2}\right)$$

5. Other markdown

At the moment, blockquotes look like this:

One is the loneliest number that you ever knew
Two can be as bad as one, it’s the loneliest number since the number one