knitr_expand.Rmd

---
title: "Untitled"
output: bookdown::html_document2
---

```{r setup, include=FALSE}
knitr::opts_chunk$set(
	echo = FALSE,
	message = FALSE,
	warning = FALSE
)
library(tidyverse)
library(gapminder)
library(knitr)
```

# The function

This function generates the scatter plots

```{r}
gapminder_continent_scatter <- function(continent){
  
  gg_scatter <- gapminder %>% 
    filter(continent == {{continent}},
           year == 1952) %>% 
    ggplot(aes(x = pop,
               y = gdpPercap)) +
    geom_point()
  
  ggsave(str_glue("gapminder_{tolower(continent)}_scatter.png"),
         gg_scatter,
         width = 6,
         height = 3)
  
}
walk(unique(gapminder$continent), gapminder_continent_scatter)
```

# Manual

## Explanation

I want to programmatically generate code chunks as follows, so that I can use internal cross-referencing properly.

- This bullet refers to the figure for Africa correctly: Figure \@ref(fig:gg-gapminder-africa-scatter) 

I would manally use this code (commented out for simplicity):

<!-- # ```{r gg-gapminder-europe-scatter, fig.cap="Scatter plot for Europe"} -->
<!-- # knitr::include_graphics("gapminder_europe_scatter.png") -->
<!-- # ``` -->
<!-- #  -->
<!-- # ```{r gg-gapminder-africa-scatter, fig.cap="Scatter plot for Africa"} -->
<!-- # knitr::include_graphics("gapminder_africa_scatter.png") -->
<!-- # ``` -->
<!-- #  -->
<!-- # ```{r gg-gapminder-oceania-scatter, fig.cap="Scatter plot for Oceania"} -->
<!-- # knitr::include_graphics("gapminder_oceania_scatter.png") -->
<!-- # ``` -->

# Programmatic Insertion

To programmatically insert these we need `knitr::knit_expand()` and the (annoying) step of inlining the code afterwards.

Thanks to this [stackoverflow answer](https://stackoverflow.com/a/14368148/1659890) for help!

```{r, results='asis'}
src <- map(levels(unique(gapminder$continent)), function(continent)
  knit_expand(text = c(
    "```{r gg-gapminder-{{tolower(continent)}}-scatter, fig.cap='Scatter plot for {{continent}}'}",
    "knitr::include_graphics('gapminder_{{tolower(continent)}}_scatter.png')",
    "```"
  )))
```

`r knit(text = unlist(src))`