Loop over .Rmd chunks

diamonds_template.Rmd

```{r diamonds_{{color}}_{{cut}}_plot}
diamonds %>% 
  filter(
    color == "{{color}}",
    cut   == "{{cut}}"
    ) %>% 
  ggplot(aes(carat, price, colour = clarity)) + 
  geom_point(show.legend = FALSE) + 
  labs(
    title = 'Price by carat for diamonds with color {{color}} and cut {{cut}}'
  )
```

index.Rmd

```{r}
library(ggplot2)
library(dplyr)

loop_over_chunks <- function(ranges, chunk_path) {
  combinations   <- do.call(expand.grid, ranges)
  variable_names <- names(ranges)
  
  lapply(seq_len(nrow(combinations)), function(i) {
    lapply(seq_along(variable_names), function(j) {
      assign(variable_names[j], combinations[i, j], pos = 1)
    }) 
    knitr::knit_expand(chunk_path)
  }) %>% 
    unlist()
}
```


```{r}
ranges <- list(
  color = c("E", "J", "I"),
  cut   = c("Ideal", "Premium", "Good", "Very Good")
)

diamond_plots <- loop_over_chunks(ranges, "diamonds_template.Rmd")
```


`r paste(knit(text = diamond_plots), collapse = '\n')`