This piece of code produces a graphic that depicts trends in contributions to UN peacekeeping on the African continent, by continent. It uses data from http://www.providingforpeacekeeping.org/contributions/

PKOcontributionsToAfrica_bycontinent.R

# install the following packages

library(scales)
library(ggplot2)
library(reshape)
library(Cairo)
library(RColorBrewer)

################
# Prepare data #
################

pko <- read.table("./data/Data.Full.csv", header=TRUE, sep=",")
pko$date <- as.POSIXct(pko$date)
pko <- pko[pko$date < as.POSIXct("2013-01-01"), ]
pko <- pko[pko$date > as.POSIXct("1990-12-31"), ]

# aggregate data for African contributions to PKOs 
aggWorld <- aggregate(total ~ date, 
                      data = pko[pko$mission.continent=="Africa", ], 
                      FUN = sum)
aggContinents <- aggregate(total ~ date + tcc.continent, 
                           data = pko[pko$mission.continent=="Africa", ], 
                           FUN = sum)
aggContinents$date <- as.POSIXct(aggContinents$date)

########
# Plot #
########

# tiny function for correct large number notation in German
point <- function(x, ...) { 
  format(x, ..., big.mark = ".", scientific = FALSE, trim = TRUE)
}

plot <- ggplot(aggContinents, aes(x=date, y=total, group=tcc.continent, fill=tcc.continent))
plot <- plot + geom_area()
plot <- plot + scale_fill_brewer(name="Kontinente",
                                 palette="Spectral")
plot <- plot + labs(title="Truppenbeiträge zu VN Friedensoperationen in Afrika nach Kontinenten\n 1991 - 2012 \n", x="", y="Truppenstärke") 
plot <- plot + theme_bw(base_size=22)
plot <- plot + theme(axis.text.x=element_text(hjust=1.1, angle=45), 
                     axis.title.y=element_text(vjust=0.3),
                     axis.title.x=element_text(size=11, lineheight=15, vjust=-.7, hjust=0))
plot <- plot + scale_y_continuous(labels = point)
plot <- plot + scale_x_datetime(limits=c(min(aggContinents$date), max(aggContinents$date)), 
                                breaks=date_breaks("years"), 
                                expand=c(.01,.01),
                                labels = date_format("%Y"))

CairoPNG(width=1280, height=800, file="PKOTCCToAfricaByContinent.png")
print(plot)
dev.off()