Reproduce Minard's March on Moscow Graphic using ggplot2

minard-plot.R

#' # Reproduce Minard's March on Moscow Graphic using ggplot2

#' This gist extends the examples given in the HistData package. It explicitly
#' shows the construction of the plot as layers, and adds the plot of temperature
#' vs. longitude below the plot of troop strength.

#' ## Load data and required packages
data(Minard.troops, package="HistData")
data(Minard.cities, package="HistData")
data(Minard.temp, package="HistData")
 
require(ggplot2)
require(scales)
require(gridExtra)

#' ## plot path of troops, and another layer for city names
 plot_troops <- ggplot(Minard.troops, aes(long, lat)) +
		geom_path(aes(size = survivors, colour = direction, group = group),
                 lineend = "round", linejoin = "round")
 plot_cities <- geom_text(aes(label = city), size = 4, data = Minard.cities)
 
#' ## Combine these, and add scale information, labels, etc.
#' Set the x-axis limits for longitude explicitly, to coincide with those for temperature

 breaks <- c(1, 2, 3) * 10^5 
 plot_minard <- plot_troops + plot_cities +
 		scale_size("Survivors", range = c(1, 10), 
 		            breaks = breaks, labels = scales::comma(breaks)) +
    scale_color_manual("Direction", 
                       values = c("grey50", "red"), 
                       labels=c("Advance", "Retreat")) +
    coord_cartesian(xlim = c(24, 38)) +
    xlab(NULL) + 
    ylab("Latitude") + 
    ggtitle("Napoleon's March on Moscow") +
    theme_bw() +
    theme(legend.position=c(.8, .2), legend.box="horizontal")
 
#' ## plot temperature vs. longitude, with labels for dates
plot_temp <- ggplot(Minard.temp, aes(long, temp)) +
	geom_path(color="grey", size=1.5) +
	geom_point(size=2) +
	geom_text(aes(label=date)) +
	xlab("Longitude") + ylab("Temperature") +
	coord_cartesian(xlim = c(24, 38)) + 
	theme_bw()
	

#' The plot works best if we  re-scale the plot window to an aspect ratio of ~ 2 x 1
 windows(width=10, height=5)

#' Combine the two plots into one
grid.arrange(plot_minard, plot_temp, nrow=2, heights=c(3,1))