In preparation for a R Workgroup meeting, I started thinking about what would be my "Top 5 R Functions". I ruled out the functions for basic mechanics - save, load, mean, etc. - they‘re obviously critical, but every programming language has them, so there‘s nothing especially "R" about them. I also ruled out the fancy statistical analysis functions like (g)lmer -- most people (including me) start using R because they want to run those analyses so it seemed a little redundant. I started using R because I wanted to do growth curve analysis, so it seems like a weak endorsement to say that I like R because it can do growth curve analysis. No, I like R because it makes (many) somewhat complex data operations really, really easy. Understanding how take advantage of these R functions is what transformed my view of R from purely functional (I need to do analysis X and R has functions for doing analysis X) to an all-purpose tool that allows me to do data processing, management, analysis, and visualization extremely quickly and easily. So, here are the 5 functions that did that for me:

1. subset() for making subsets of data (natch)
2. merge() for combining data sets in a smart and easy way
3. melt() for converting from wide to long data formats
4. dcast() for converting from long to wide data formats, and for making summary tables
5. ddply() for doing split-apply-combine operations, which covers a huge swath of the most tricky data operations 

My "Top 5 R Functions"（转）