Here is the picture, 'plot2.png"
Here is the picture, "plot3.png".
Here is the picture, "plot4.png".
Here is the code for "plot1.R"
Here is the code for "plot2.R"
Here is the code for "plot3.R"
Here is the code for "plot4.R"
here is plot1
Merge branch 'master' of https://github.com/zzwhe/ExData_Plotting1