install.packages can't be used to update single packages
various fixes correcting typos, nomenclature, etc
The relative path used is a full path. Changed it to loose the first `/` but you may prefer `./` instead.

A session history isn't a problem, it is the image `.RData` file that is the problem.
Minor changes. Library -> Package.
Some more minor tweaks, formatting etc.
Various tweaks

 * preferred if you quote package names in `library()`
 * replaced `=` with `<-`
 * consistency changes
 * reformatted some of the code blocks to line up the inline sections
Make is clear that this `seq()` call is using `x` as argument `along`, which won't be very clear for new users.
Merged in Gavin's changes