ggplot2BoxplotGrouping.R

#A solution with ggplot2

#library(reshape2)
#test.m <- melt(test)

#sample of dataframe:
head(combined.data)
>  region expression species
1    NAc  0.4711284 macaque
2    NAc -0.1003201 macaque
3     Pu -0.3629559 macaque
4   Caud -0.3749001 macaque
5    GPe -0.5241925 macaque
6    GPi -0.5855168 macaque

#Plot the data:

ggplot(combined.data, aes(x = region, y = expression, fill = species)) +
+     geom_boxplot() +
+     scale_fill_manual(values = c("yellow", "orange"))
+     ggtitle("MAOA expression in human vs. macaque")
+     theme(axis.text.x = element_text(angle=90, face="bold", colour="black"))

#http://stackoverflow.com/questions/14608422/box-plots-for-groups
#http://stackoverflow.com/questions/7883190/how-to-display-two-groups-of-boxplots