R: Patterns to match and extract R code in a document

knit_patterns {knitr} | R Documentation

## Patterns to match and extract R code in a document

### Description

Patterns are regular expressions and will be used in functions like `grep` to extract R code and chunk options. The object `knit_patterns` controls the patterns currently used; see the references and examples for usage. All built-in patterns are available in the list all_patterns.

### Usage

    knit_patterns

### Format

An object of class `list` of length 5.

### References

Usage: https://yihui.name/knitr/objects/

Components in `knit_patterns`: https://yihui.name/knitr/patterns/

### See Also

`all_patterns`

### Examples

    library(knitr)
    opat = knit_patterns$get()  # old pattern list (to restore later)

    apats = all_patterns  # a list of all built-in patterns
    str(apats)
    knit_patterns$set(apats[["rnw"]])  # set pattern list from apats

    knit_patterns$get(c("chunk.begin", "chunk.end", "inline.code"))

    # a customized pattern list; has to empty the original patterns first!
    knit_patterns$restore()
    # we may want to use this in an HTML document
    knit_patterns$set(list(chunk.begin = "<!--helloR\\s+(.*)", chunk.end = "^byeR-->"))
    str(knit_patterns$get())

    knit_patterns$set(opat)  # put the old patterns back

[Package knitr version 1.20 Index]