swcarpentry/bc — pull request #857 by fmichonneau (2014-11-14 23:25:14+00:00)
Title: Add na

Summary of modifications:

- removing trailing spaces
- renamed/reformatted/restructured headers to make them clearer and coherent with rest of document
- removed duplicated examples
- demonstrated how to add elements also in the front of vectors
- added section about NA (missing values)
- attempted to clarify section about coercion