+.ggplot: Modify a plot by adding on new components.
Description
What happens when you add on:Usage
## S3 method for class 'ggplot':
+(p, object)
Details
- data.frame: replace current
  data.frame (must use- %+%)
- uneval:
  replace current aesthetics
- layer: add new
  layer
- options: update plot options
- scale: replace current scale
- coord:
  override current coordinate system
- facet:
  override current coordinate faceting