11.10 Reformat R source code

11.10 Reformat R source code

When you set the chunk option tidy = TRUE, the R source code will be reformatted by the tidy_source() function in the formatR package (Xie 2019a). The tidy_source() can reformat the code in several aspects, such as adding spaces around most operators, indenting the code properly, and replacing the assignment operator = with <-. The chunk option tidy.opts can be a list of arguments to be passed to formatR::tidy_source(), e.g.,

```{r, tidy=TRUE, tidy.opts=list(arrow=TRUE, indent=2)}
## messy R code...
1+            1
x=1:10#some users prefer '<-' as the assignment operator
if(TRUE){
print('Hello world!') # indent by 2 spaces
}

The output:

messy R code...

1 + 1 x <- 1:10 #some users prefer ‘<-’ as the assignment operator if (TRUE) { print(“Hello world!”) # indent by 2 spaces }

In Section [5.3](/read/rmarkdown-cookbook-1.0-en/d048#text-width), we mentioned how to control the width of text output. If you want to control the width of the source code, you may try the `width.cutoff` argument when `tidy = TRUE`, e.g.,

## a long expression
1+1+1+1+1+1+1+1+1+1+1+1+1+1+1+1+1+1+1+1+1+1+1+1+
1+1+1+1+1+1+1+1+1+1+1+1+1+1+1+1+1+1+1+1+1+1+1+1

The output:

a long expression

1 + 1 + 1 + 1 + 1 + 1 + 1 + 1 + 1 + 1 + 1 + 1 + 1 + 1 + 1 + 1 + 1 + 1 + 1 + 1 + 1 + 1 + 1 + 1 + 1 + 1 + 1 + 1 + 1 + 1 + 1 + 1 + 1 + 1 + 1 + 1 + 1 + 1 + 1 + 1 + 1 + 1 + 1 + 1 + 1 + 1 + 1 + 1

Please read the help page `?formatR::tidy_source` to know the possible arguments, and also see [https://yihui.org/formatR/](https://yihui.org/formatR/) for examples and limitations of this function.

Alternatively, you may use the **styler** package (Müller and Walthert 2020) to reformat your R code if you set the chunk option `tidy = 'styler'`. The R code will be formatted with the function `styler::style_text()`. The **styler** package has richer features than **formatR**. For example, it can align function arguments and works with the pipe operator `%>%`. The chunk option `tidy.opts` can also be used to pass additional arguments to `styler::style_text()`, e.g.,

## align the assignment operators
a   <- 1#one variable
abc <- 2#another variable

```

By default, tidy = FALSE and your R code will not be reformatted.

References

Müller, Kirill, and Lorenz Walthert. 2020. Styler: Non-Invasive Pretty Printing of r Code. https://github.com/r-lib/styler.

———. 2019a. formatR: Format r Code Automatically. https://github.com/yihui/formatR.