The levels section was using a level "NA" together with "female" and "male", which is misleading (given that NA was just introduced as a missing value). I updated it to what I believe is a better example of how NAs are interpreted.
Additionally, I edited a comment about Inf that wouldn't compile. How about inserting it at the tutorial altogether?
Minor changes to comments (fixing typos, etc.). Deleted "weird types" section; broke out "NULL" type into its own type category. Added instructions for dropping rows and columns in data.frame and data.table. How to make summary tables in data.table.
I moved some things around. I preserved isomorphismes' "no programming knowledge first" approach; I really like this. In the "programming-heavy" part of the tutorial, I emphasized from the very beginning that every "single" thing in R, like 4 or "foo", is really just a vector of length 1. I added in some whirlwind tours of data.table and ggplot2.
Fixed a problem with the jiggle function - variable x wasn't being updated before being returned, and the rnorm function was being asked to return x output values, rather than one.
After testing, the values given the documentation are now correct.
significant changes. style changes (no !, no =>). content additions. start by showing off R's non-programming features before getting to the language per se.
Fixed the mistake about integers that yuhui brought up. Deleted the confusing suggestion about command-enter (doesn't work for all GUIs or on Windows). Added some more information about vectors. Added some information about conditional clauses. Included some information at the very end on where to get R and R GUIs
