sample_data_phones_films.R

set.seed(1234)
dat <- data.frame(
  product=c(rep("Mobile",2),
            rep(c("Smartphone", "Mobile"),3),
            rep(c("Video rental shop"),3),
            rep(c("Video rental shop", 
                  "Online movie rental"),2)),
  year=c(2008:2010, 2010, 2011, 2011, 2012, 2012,
         2008:2010, 2011, 2011, 2012, 2012),
  category=c(rep("Phone", 8), rep("Film", 7)),
  price.change=rnorm(15, 0, 0.1)+0.1)

dat$product <- with(dat, factor(product, 
                    levels=levels(product)[c(1,3,4,2)],
                    ordered=TRUE))
library(lattice)
my.settings <- canonical.theme(color=FALSE)
my.settings[['strip.background']]$col <- "black"
my.settings[['strip.border']]$col<- "black"       
barchart(price.change ~ factor(year) | product, 
         data=dat, 
         layout=c(2,2),
         par.settings = my.settings, 
         par.strip.text=list(col="white", font=2),                
         horizontal=FALSE, origin=0, 
         scales=list(cex=c(1.1, 1.1)), # increase font size
         xlab=list(label="Year", fontsize=14),
         ylab=list(label="Price change", fontsize=14),
         panel=function(x,y,...){
           panel.abline(h=0)
           panel.barchart(x,y,...)
         })