plotgap

pushViewport(viewport(layout = grid.layout(2, 1, heights = unit(c(1,1), "null"))))
theme_set(theme_bw())
plot.both = ggplot(data = data) + geom_line(aes(x = date, y = buy),linetype = 1) +
                                 geom_line(aes(x = date, y = sell),linetype = 3) +
                                 xlab("") + ylab("Weighted Average Price") + 
                                 ylim(range(cbind(data$buy, data$sell))[1],range(cbind(data$buy, data$sell))[2]) +
                                 ggtitle(paste(c("ETF ID:", etf.id, " (",etf.sym,")"), collapse = "")) +
                                 theme(
                                 legend.position = "none",
                                 axis.title = element_text(size = 10),
                                 axis.text = element_text(size = 9)
                                 )
plot.spread = ggplot(data = data, aes(x = date, y = spread, colour = ID)) + geom_line() + 
                                 xlab("Year 2014") + ylab("Buy-Sell Spread (%)") + 
                                 ylim(range(data$spread)[1], range(data$spread)[2]) +
                                 theme(
                                 legend.position = "none",
                                 axis.title = element_text(size = 10),
                                 axis.text = element_text(size = 9)
                                 ) +
                                 geom_hline(yintercept = 0, linetype = "dashed")
print(plot.both, vp = viewport(layout.pos.row = 1, layout.pos.col = 1:1))
print(plot.spread, vp = viewport(layout.pos.row = 2, layout.pos.col = 1:1))