plot0 creates all 4 figures for screen
plot1 reads data file, creates data frame, generates figure1
plot2 & plot3 use data frame created by plot1, generate figures 2 and 3
revise code for lower-left figure to reflect changes in plot3.R
	i.e., use of a vector for colors to guarantee legend uses correct colors
insert a  setwd()  command to assure work is done in correct location
omit ' (kilowatts)' from upper-left figure in plot4
plot4 after cosmetic revisions to left pair of figures
    upper-left:  omit  ' (kilowatts)'  from ylab
    lower-left:  omit frame around legend
symbolic link to actual file in  ../data
the four image files which the assignment requires be pushed into the remote repo for view during peer-grading
console log of plot1.R
  includes several warning messages
1)	revised title: summary ...
2)	document full process: download data, project repo, symbolic link to data
3)	minor revision of some intermediate comments
4)	end with several toDo
append commands for alternative initial processing