The Cologne R user group met last Friday for two talks on split apply combine in R and XLConnect by Bernd Weiß and Günter Faes respectively, before the usual Schnitzel and Kölsch at the Lux. Split apply combine in R

The apply family of functions in R is incredible powerful, yet for newcomers often somewhat mysterious. Thus, Bernd gave an overview of the different apply functions and their cousins. The various functions differ in their object inputs, e.

The ave function in R is one of those little helper function I feel I should be using more. Investigating its source code showed me another twist about R and the “[” function. But first let’s look at ave.
The top of ave’s help page reads:
Group Averages Over Level Combinations of Factors
Subsets of x[] are averaged, where each subset consist of those observations with the same factor levels.