knitr (version 1.48)

convert_chunk_header: Convert the in-header chunk option syntax to the in-body syntax

Description

This is a helper function for moving chunk options from the chunk header to the chunk body using the new syntax.

Usage

convert_chunk_header(
  input,
  output = NULL,
  type = c("multiline", "wrap", "yaml"),
  width = 0.9 * getOption("width")
)

Value

A character vector of converted input when output = NULL. The output file path with converted content otherwise.

Arguments

input

File path to the document with code chunks to convert.

output

The default NULL will output to console. Other values can be a file path to write the converted content into or a function which takes input as argument and returns a file path to write into (e.g., output = identity to overwrite the input file).

type

This determines how the in-body options will be formatted. "mutiline" (the default, except for qmd documents, for which the default is "yaml") will write each chunk option on a separate line. Long chunk option values will be wrapped onto several lines, and you can use width = 0 to keep one line per option only. "wrap" will wrap all chunk options together using base::strwrap(). "yaml" will convert chunk options to YAML.

width

An integer passed to base::strwrap() for type = "wrap" and type = "multiline". If set to 0, deactivate the wrapping (for type = "multiline" only).

About <span class="pkg">knitr</span> option syntax

Historical chunk option syntax have chunk option in the chunk header using valid R syntax. This is an example for .Rmd document

```{r, echo = FALSE, fig.width: 10}
```

New syntax allows to pass option inside the chunk using several variants

• Passing options one per line using valid R syntax. This corresponds to convert_chunk_header(type = "multiline").

  
  ```{r}
  #| echo = FALSE,
  #| fig.width = 10
  ```
  

• Passing option part from header in-chunk with several line if wrapping is needed. This corresponds to convert_chunk_header(type = "wrap")

  
  ```{r}
  #| echo = FALSE, fig.width = 10
  ```
  

• Passing options key value pairs in-chunk using YAML syntax. Values are no more R expression but valid YAML syntax. This corresponds to convert_chunk_header(type = "yaml") (not implement yet).

  ```{r}
  #| echo: false,
  #| fig.width: 10
  ```
  

Examples

knitr_example = function(...) system.file("examples", ..., package = "knitr")
# Convert a document for multiline type
convert_chunk_header(knitr_example("knitr-minimal.Rmd"))
# Convert a document for wrap type
convert_chunk_header(knitr_example("knitr-minimal.Rmd"), type = "wrap")
# Reduce default wrapping width
convert_chunk_header(knitr_example("knitr-minimal.Rmd"), type = "wrap", width = 0.6 *
    getOption("width"))
if (FALSE) {
# Explicitly name the output
convert_chunk_header("test.Rmd", output = "test2.Rmd")
# Overwrite the input
convert_chunk_header("test.Rmd", output = identity)
# Use a custom function to name the output
convert_chunk_header("test.Rmd", output = \(f) sprintf("%s-new.%s",
    xfun::sans_ext(f), xfun::file_ext(f)))
}