This tutorial is the third in a series of R tutorials. It introduces basic R programming, debugging and optimization techniques and develops practices of proper and efficient R coding. It covers the following topics: o if-else and switch statements o types of loops (for, while, repeat) and loop control statements (next, break) o user functions and argument definitions o local and global variables o apply function family o sourcing, timing, compilation and debugging o code profiling and optimization Prerequisite: We strongly recommend that you also register for the “Introduction to R” tutorial if you are new to the R environment.