R Markdown - variable output name

This is pretty much what I do:

rmarkdown::render('my_markdown_report.Rmd',
                  output_file = paste('report.', Sys.Date(), 
                                      '.pdf', sep=''))

I have three scripts - one pulls the data and process it, second created charts & tables for report. Third one creates report based on markdown file. Code you see above is the part of the third script

You can keep the simplicity of using the RStudio Knit button and reproducibility of a YAML header by using the undocumented knit hook to redefine what the button does (default function called is rmarkdown::render). The output_file parameter of the render function specifies the file name, so by setting it you override the standard behaviour of using the same prefix as the input filename.

e.g. to always output a file called myfile.pdf

knit: (function(inputFile, encoding) { rmarkdown::render(inputFile, encoding = encoding, output_file = file.path(dirname(inputFile), 'myfile.pdf')) })

The function can be an anonymous one-liner as well as imported from a package, as seen here with slidify.

You can set your own YAML headers (I don't know if this is generally advised anyway), accessible under rmarkdown::metadata$newheader but they don't seem available from within this sort of function as far as I can see.

As for passing file name in from an R chunk... if you're referring to code chunks below the YAML header, from my experience I don't think that's possible(?). Headers can contain inline R commands (single backtick-enclosed, starting with r), but seemingly not for this hook function.

Related:

• Rmarkdown GitHub repo issue — output format-specific output_file
• Blog post I wrote following this question [invalid link, domain for sale as of 20210216] / corresponding GitHub wiki notes