I produce the folowing two lines with ggplot and would like to shade a specific region between the two lines i.e. where y=x² is greater than y=2x, where 2 <= x <= 3.
# create data #
x<-as.data.frame(c(1,2,3,4))
colnames(x)<-"x"
x$twox<-2*x$x
x$x2<-x$x^2
# Set colours #
blue<-rgb(0.8, 0.8, 1, alpha=0.25)
clear<-rgb(1, 0, 0, alpha=0.0001)
# Define region to fill #
x$fill <- "no fill"
x$fill[(x$x2 > x$twox) & (x$x <= 3 & x$x >= 2)] <- "fill"
# Plot #
ggplot(x, aes(x=x, y=twox)) +
geom_line(aes(y = twox)) +
geom_line(aes(y = x2)) +
geom_area(aes(fill=fill)) +
scale_y_continuous(expand = c(0, 0), limits=c(0,20)) +
scale_x_continuous(expand = c(0, 0), limits=c(0,5)) +
scale_fill_manual(values=c(clear,blue))
The result is the following which just shades the region under the line y=2x, and this no matter what the x-value - why?
How about using geom_ribbon
instead
ggplot(x, aes(x=x, y=twox)) +
geom_line(aes(y = twox)) +
geom_line(aes(y = x2)) +
geom_ribbon(data=subset(x, 2 <= x & x <= 3),
aes(ymin=twox,ymax=x2), fill="blue", alpha=0.5) +
scale_y_continuous(expand = c(0, 0), limits=c(0,20)) +
scale_x_continuous(expand = c(0, 0), limits=c(0,5)) +
scale_fill_manual(values=c(clear,blue))