geom_smooth behaves like geom_path

[izahn]

I noticed that geom_smooth behaves like geom_path rather than geom_line. For example,

library(ggplot2)

ggplot(transform(mtcars, 
                 pred.mpg = predict(lm(mpg ~ poly(hp, 2), 
                                       data = mtcars), 
                                    interval = "confidence"))) + 
  geom_smooth(aes(x = hp,
                  y = pred.mpg.fit, 
                  ymin = pred.mpg.lwr, 
                  ymax = pred.mpg.upr), 
              stat = "identity")

produces

Whereas ordering by the x-axis variable produces the desired result:

ggplot(transform(mtcars, 
                 pred.mpg = predict(lm(mpg ~ poly(hp, 2), 
                                       data = mtcars), 
                                    interval = "confidence"))[order(mtcars$hp), ]) + 
  geom_smooth(aes(x = hp,
                  y = pred.mpg.fit, 
                  ymin = pred.mpg.lwr, 
                  ymax = pred.mpg.upr), 
              stat = "identity")

I looked at the geom_smooth code, but I don't understand why it behaves this way. It looks like GeomSmooth calls GeomLine, and GeomLine does

  setup_data = function(data, params) {
    data[order(data$PANEL, data$group, data$x), ]
  }

so I would have thought ordering the data myself would make no difference.

[hadley]

It probably just calls the draw method, not the setup_data() method.

[izahn]

Thanks, I've submitted #2029 to address this.