- read data
- build histogram
- build histogram
- plot1
- load data
- fix comment in Plot1
- add plot to Plot2
- add plot2.png
- draw three plots
- add all plots and legent
- add plot3
- use more functions
- reset graphics device
- add plot 4
- fixes for plot4
- fixed all png files by saving directly into png file (instead of copying from screen)
- fix error in 3rd plot in plot4
- remove unused comments