Create inset graphs in ggplot2

insetgraphs.R

library(ggplot2)
library(grid)

# A viewport taking up a fraction of the plot area
vp <- viewport(width = 0.4, height = 0.4, x = 0.1, y = 0.9,just=c("left","top"))

b_plot <- ggplot(cars,aes(speed,dist))+geom_line()+xlim(10,15)
b_plot

# Just draw the plot twice
# First approach
png("test.png")
print(b_plot)
print(a_plot, vp = vp)
dev.off()

# Second approach
# A function to plot both graphs on the same windows
 full <- function() {
  print(b_plot)
  theme_set(theme_bw(base_size = 8))
  theme_white()
  print(a_plot, vp = vp)
  theme_set(theme_bw())
}