Motivation Lately, I, Edward, have been programming in Julia a lot. Two times in the last week, I’ve needed a function like R’s tapply(), but in Julia. With a little bit of searching around the interwebs, I hacked together a reasonable equivalent to R’s tapply() written in Julia. This blog post will explain the function tapply() and briefly introduce the two examples where I used tapply(). Last, I’ll provide my Julia code which replicates R’s tapply() function.