Add text outside the chart area of a ggplot2 graph in R and save the resulting chart to a png file.

saveChart.R

require(ggplot2)
require(gridExtra)

saveChart <- function(chart, fileName) {
  # Draw attribution.
  chart <- chart + geom_text(aes(label = 'sentimentview.com', x = 2.5, y = 0), hjust = -2, vjust = 6, color="#a0a0a0", size=3.5)
  
  # Disable clip-area.
  gt <- ggplot_gtable(ggplot_build(chart))
  gt$layout$clip[gt$layout$name == "panel"] <- "off"
  grid.draw(gt)
  
  # Save chart.
  ggsave <- ggplot2::ggsave; body(ggsave) <- body(ggplot2::ggsave)[-2]
  chart <- arrangeGrob(gt)
  ggsave(fileName, chart)  
}

data <- data.frame(name = c('Company A', 'Company B', 'Company C', 'Company D'), age = sample(1:4))
g <- ggplot(data=data, aes(x=name, y=age)) + xlab("Company") + ylab('Years') + ggtitle('Something Nifty') + geom_bar(stat='identity') + theme_bw()

saveChart(g, "chart.png")

vchart.png

To make this work, I had to add require( grid ) so that the call to grid.draw would resolve.