Add "data manipulation/aggregation".
Add "efficient programming".
Add "object oriented programming".
Config.
Create a folder for general R notes.
Add "string manipulation" and "code evaluation".
Graphics folder: base, lattice, ggplot2.
Update, and use only Iris dataset for examples.
Add "Package construction".
Added negative subsetting of data frames.
Add "workspace management".
Add miscellaneous notes, as I don't know how to organize this section yet.
Add exporting functions.
Update merge()
Add "Input/output".