title: Is there any way to set the line end style or the line join style in ggplot?
body: <p>For a description of the line end and line join styles available in R, see
  <a href="http://students.washington.edu/mclarkso/documents/line%20styles%20Ver2.pdf">http://students.washington.edu/mclarkso/documents/line%20styles%20Ver2.pdf</a></p>
  
  <p>For ggplot, I already searched in plot_theme() and the github list of ggplot2 opts <a href="https://github.com/hadley/ggplot2/wiki/%2Bopts%28%29-List">https://github.com/hadley/ggplot2/wiki/%2Bopts%28%29-List</a> but found no leads, so I'm thinking it's not possible to change these in ggplot.</p>