plot4.R

# lattice of four plots
# 
# Panel 1 (upper left) - replica of plot 2
# Panel 2 (upper right) - line graph
# 	x axis: datetime
# 		min: thu
# 		max: sat
# 	y axis: voltage
# 		min: 234
# 		max: 246
# 	line colour: black
# Panel 3 (lower left) - replica of plot 3
# Panel 4 (lower right) - line graph
# 	x axis: day of week
# 		min: thu
# 		max: sat
# 	y axis: global reactive power
# 		min: 0.0
# 		max: 0.5
# 	line colour: black