R: ggplot - Plotting multiple variables on a line chart

In my continued playing around with meetup data I wanted to plot the number of members who join the Neo4j group over time. I wanted to plot the actual count alongside a rolling average for which I created the following data frame:



from dzone.com: latest front page http://www.dzone.com/links/r/r_ggplot_plotting_multiple_variables_on_a_line_ch.html