Ignore data/ directory
Add script to download the reference data
Add first plot script (plot1.R) and resulting PNG image (plot1.png)
Add second plot script (plot2.R) and resulting PNG image (plot2.png)
Add third plot script (plot3.R) and resulting PNG image (plot3.png)
Add fourth and final plot script (plot4.R) and resulting PNG image (plot4.png)