title: ggplot2 polar plot axis label location
body: <p>This is just a extension for a old question
  <a href="https://stackoverflow.com/questions/10515703/ggplot2-polar-plot-arrows">ggplot2 polar plot arrows</a>
  <img src="https://i.stack.imgur.com/diRdi.gif" alt="Compass plot from MatLab"></p>
  
  <p>You will find the x axis is out of the most_out circle.
  In ggplot2, I use "panel.grid.major =  theme_line(colour = "black", size = 0.2, linetype=2)" to get the dashed circle, just as below:
  <img src="https://i.stack.imgur.com/HzYcQ.png" alt="using GGplot2">
  So my question is how to make the axis label (180, 135, 90, .....) outside of the circle, because the text are merge with the circular lines.</p>
  
  <p>I try to use "hjust" or "vjust" to adjust the distance between text and axis. But it does not work.
  So do you have some ideas about this problem?
  Thanks first!!!!</p>