title: How to change the glyph or icon for geom_abline in the legend?
body: <p>Im following this example <a href="https://stackoverflow.com/questions/46760519/add-regression-line-legend-to-geom-abline">Add regression line legend to geom_abline</a></p>
  
  <p>Is there a reason the legend line is slanting? Is it possible for the legend to have a straight red and blue line? </p>