ggsubplot allows embedding of one ggplot in another. Variants of this are commonly requested, although often separate plots are better. Package is quite slow. ggsubplot uses but does not include code for map_afghanistan and map_americas layers, which are included here.

demo_ggsubplot.R

##
## Vignette code for ggsubplot with needed map_afghanistan and map_americas layers
## matt@baggott.net
## Dec 16, 2012

# install.packages("ggsubplot")

library(ggplot2)
library(ggsubplot)
library(maps)
library(plyr)

# getbox by Heike Hoffman, 
# https://github.com/ggobi/paper-climate/blob/master/code/maps.r
getbox <- function (map, xlim, ylim) {
  # identify all regions involved
  small <- subset(map, (long > xlim[1]) & (long < xlim[2]) & (lat > ylim[1]) & (lat < ylim[2]))
  regions <- unique(small$region)
  small <- subset(map, region %in% regions)  

  # now shrink all nodes back to the bounding box
  small$long <- pmax(small$long, xlim[1])
  small$long <- pmin(small$long, xlim[2])
  small$lat <- pmax(small$lat, ylim[1])
  small$lat <- pmin(small$lat, ylim[2])

  # Remove slivvers
  small <- ddply(small, "group", function(df) {
    if (diff(range(df$long)) < 1e-6) return(NULL)
    if (diff(range(df$lat)) < 1e-6) return(NULL)
    df
  })

  small
}


## map layer
## adapted from map_nasa:
# https://github.com/ggobi/paper-climate/blob/master/code/maps.r

# assembling data
world <- map_data("world")
states <- map_data("state")
states$group <- max(world$group) + states$group
both <- rbind(world, states)
americas <- getbox(both, xlim = c(-115, -55), ylim = c(-21.1, 36.6))

# building americas layer
map_americas <- list(
  geom_polygon(aes(long, lat, group = group), data = americas, fill = "grey70", 
               colour = "grey60", inherit.aes = FALSE, show_guide = FALSE),
  scale_x_continuous("", breaks = NULL, expand = c(0.02, 0)),
  scale_y_continuous("", breaks = NULL, expand = c(0.02, 0)))


# building afghanistan layer
afghanistan <- getbox(world, c(60,75), c(28, 39))
map_afghanistan <- list(
  geom_polygon(aes(long, lat, group = group), data = afghanistan, 
               fill = "white", colour = "black", inherit.aes = FALSE, 
               show_guide = FALSE),
  scale_x_continuous("", breaks = NULL, expand = c(0.02, 0)),
  scale_y_continuous("", breaks = NULL, expand = c(0.02, 0)))


## Afghan War Journal raw data

ggplot(casualties) +
   map_afghanistan +
   geom_point(aes(lon, lat, color = victim)) +
   coord_map()+
   theme(legend.position = "none", legend.key = element_rect(fill = 'white')) 


## 2d bin with bar chart subplots displaying data in each region
ggplot(casualties) +
   map_afghanistan +
   geom_subplot2d(aes(lon, lat,
   subplot = geom_bar(aes(victim, ..count.., fill = victim))),
   bins = c(15,12), ref = NULL, width = rel(0.8)) +
   coord_map()+
   theme(legend.position = "right")


## Stars in an embedded plot

ggplot(nasa) +
   map_americas +
   geom_subplot(aes(long, lat, group = id,
   subplot = geom_star(aes(x = 0, y = 0, r = surftemp,
   angle = date, fill = mean(surftemp)), r.zero = FALSE))) +
   coord_map()