round-3-ggplot2.r

library("Quandl")
library("ggplot2")
library("reshape2")

hist_rev <- Quandl("TPC/HIST_RECEIPT", 
  start_date = "1945-12-31", 
  end_date = "2013-12-31")

# melt into tidy (http://vita.had.co.nz/papers/tidy-data.html) form
hist_revm <- melt(hist_rev, id = "Fiscal Year")
names(hist_revm) <- c("year", "source", "pct_gdp")

# select categories of interest
income_tax <- subset(hist_revm, 
  source %in% c("Individual Income Taxes", "Corporation Income Taxes"))

qplot(year, pct_gdp, data = income_tax, colour = source) +
  geom_line() + 
  geom_smooth(method = "lm")