Bookdown markdown headers are special in that each chapter *must* start with a first-level header `#`.
checkVignette(rmdfile)
| rmdfile | character(1) path to a `.Rmd` file |
|---|
A common workflow is to have each "chapter" respresented as a single `.Rmd` file. Functions to check and then fix `.Rmd` files programmatically facilitate finding and fixing vignettes that do not meet these criteria.