The run function runs a Shiny document by starting a Shiny
  server associated with the document. The shiny_args parameter can be
  used to configure the server; see the runApp
  documentation for details.  Once the server is started, the document will be rendered using
  render. The server will initiate a render of the document
  whenever necessary, so it is not necessary to call run every time
  the document changes: if auto_reload is TRUE, saving the
  document will trigger a render. You can also manually trigger a render by
  reloading the document in a Web browser.
  The server will render any R Markdown (.Rmd) document in dir;
  the file argument specifies only the initial document to be
  rendered and viewed. You can therefore link to other documents in the
  directory using standard Markdown syntax, e.g.
  [Analysis Page 2](page2.Rmd).
  If default_file is not specified, nor is a file specified on the
  URL, then the default document to serve at / is chosen from (in
  order of preference):
  
- Ifdircontains only oneRmd, thatRmd.
- The file index.Rmd, if it exists indir
- The file index.html, if it exists indir