demonstration of plotting distributions overlapping lineplots in R

demo_distline.R

##
## demonstration of distributions overlapping on lineplots
## matt@baggott.net
## Dec 11, 2012
##
## in response to: http://stats.stackexchange.com/questions/45591/r-plot-time-indexed-densities/45614#45614

library(ggplot2)   # for plotting
library(lubridate) # for getting year from dates in dataset
library(plyr)      # for getting annual mean easily

data(economics)    # sample dataset

# calculate year to group by using lubridate's year function
economics$year <- year(economics$date)

# get a subset 
subgrp <- economics[economics$year>2001&economics$year<2007,]    

# get the mean of each year
subgrp <- ddply(subgrp, .(year), mutate, mean=mean(unemploy))

# plot
ggplot(subgrp, aes(x=date, y=unemploy))+ 
    geom_violin(aes(group=year, colour=year, fill=year), alpha=0.5, 
    kernel="rectangular")+    # passes to stat_density, makes violin rectangular 
    xlab("Year")+             # label one axis
    ylab("Unemployment")+     # label the other
    coord_flip()+             # flip the axes so violin plots are sideways
    theme_bw()+                      # make background white
    theme(legend.position="none")+   # suppress legend for year colors
    geom_line(aes(x=date, y=mean,    # add a line for the mean 
        group=year),colour="purple")+
    geom_line(size=1.5)              # make line for monthly data