Simple ggplot2 pie chart function.

piechart.R

piechart <- function(set) {
  ggplot(dat[dat$type==set,], aes(x = "", y = pageviews, fill = name)) + 
    theme_bw() +
    geom_bar(width = 1) + 
    coord_polar(theta = "y") +
    labs(y="", x='') +
    opts(panel.border = theme_rect(colour = 'white'),
         axis.text.x = theme_text(colour='white'))
}

# Where dat is our data.frame, and set is the level of a factor in a column called 'type' that you want to plot.