Adding custom CSS tags to an RMarkdown html document

Question

I have an RMarkdown document outputting to HTML of the same form as the below example. What do I add where to apply unique CSS ids or classes to each plot output?

Answer 1

Open the resultant HTML in a browser with a Developer Tools option and look at the generated HTML. Then apply you styling to the appropriate tags/classes. For example, put the following into style.css, knit the file and you should see a red border on the plots:

img {
  background-color: red;
  padding: 2px;
  border: 1px solid red;
  border-radius: 3px;
  margin: 0 5px;
  max-width: 100%;
}