Example of qqplots in ggplot2

ggplot_qqPlot.R

occlusion2.data$qqplot.comparison.resid <- ddply(.data = occlusion2.data$qqplot.comparison, .variables = .(condition, transformed), function(dat){
  q <- qqnorm(dat$threshold, plot = FALSE)
  dat$xq <- q$x
  dat
}
)

occlusion2.qqplot <- ggplot(data = occlusion2.data$qqplot.comparison.resid, aes(x = xq, y = threshold)) +
  geom_smooth(method = "lm", se = FALSE, size = 1) +
  geom_point() +
  xlab("theoretical quantiles") +
  ylab("sample quantiles") +
  facet_grid(transformed ~ condition, scales = "free") +
  theme_bw(base_size = 14)+
  theme(legend.position="none",
        panel.background = element_blank(), 
        axis.title.y = element_text(vjust=1.5),
        axis.title.x = element_text(vjust=0),
        strip.background = element_rect(fill = "black", color = "black"),
        strip.text = element_text(face = "bold", colour = "white"))