regrading adding a legend using ggplot2 for different lines

Question

I want to add a legend that will tell which color represents which line using ggplot2. My code is as follows :

require(lme4)
require(ggplot2)
m1 <         


        

Answer 1

Put the color parameter in aes and give it the name you want to show in the the legend and then choose the title and colors in scale_color_manual

Example:

library(ggplot2)

ggplot(mpg, aes(displ, hwy)) +
  geom_point() +
  geom_smooth(aes(color='Smooth 1')) +
  geom_smooth(aes(y = (hwy -1), color='Smooth 2')) +
  scale_color_manual('Legend Title', values=c('Smooth 1'='blue', 'Smooth 2'='red'))