Line Graphs - R Graphics - page 84

Solution
Use geom_area() to get a shaded area, as in Figure 4-17 :
# Convert the sunspot.year data set into a data frame for this example
sunspotyear <- data.frame(
Year = as.numeric(time(sunspot.year)),
Sunspots = as.numeric(sunspot.year)
)
ggplot(sunspotyear, aes(x = Year, y = Sunspots)) + geom_area()
Figure 4-17. Graph with a shaded area
Discussion
By default, the area will be filled with a very dark grey and will have no outline. The color can
be changed by setting fill . In the following example, we'll set it to "blue" , and we'll also make
it 80% transparent by setting alpha to 0.2. This makes it possible to see the grid lines through
the area, as shown in Figure 4-18 . We'll also add an outline, by setting colour :
ggplot(sunspotyear, aes(x = Year, y = Sunspots)) +
geom_area(colour = "black" , fill = "blue" , alpha = .2 )