RMarkdown is the dynamic document format RStudio uses. It is normal Markdown plus embedded R (or any other language) code that can be executed to produce outputs, including tables and charts, within the document. Hence, after changing your R code, you can just rerun all code in the RMarkdown file rather than redo the whole run-copy-paste cycle. And an RMarkdown file can be directly exported into multiple formats, including HTML, PDF, and Word.
Click through for the demo.