Connecting the Dots ggplot2 qplot

Question

I'm working on a homework assignment for the Coursera Exploratory Data Analysis class, and this code creates the following image:

qplot(year, Emissions, data=Baltimore_Data, 
      stat='summary', fun.y='sum', facets=.~type)

I am trying to connect the dots, and I've been trying things like:

+ geom_line()

and

+ geom_polygon()

and lots of other things to no avail. For what it's worth, I already met the intent without the lines, I just wanted to make it prettier and it bothers me that I can't figure it out!

Answer 1

You need to aggregate outside of ggplot or use stat_summary twice (which is somewhat wasteful for bigger datasets):

ggplot(Baltimore_Data, aes(x = year, y= Emissions)) +
  stat_summary(fun.y = sum, geom = "point") +
  stat_summary(fun.y = sum, geom = "line") +
  facet_grid(. ~ type)

(Not tested because there is no reproducible example in the question.)