The magrittr package offers a set of operators which promote semantics
that will improve your code by

* structuring sequences of data operations left-to-right (as
  opposed to from the inside and out),
* avoiding nested function calls,
* minimizing the need for local variables and function
  definitions, and
* making it easy to add steps anywhere in the sequence of operations.

WWW: http://cran.r-project.org/web/magrittr/