Data Analysis with R, Second Edition - Second Edition

Be smart about your code

In many cases, the performance of the R code can be greatly improved by simple restructuring of the code; this doesn't change the output of the program, just the way it is represented. Restructurings of this type are often referred to as code refactoring. The refactorings that really make a difference performance-wise usually have to do with either improved allocation of memory or vectorization.