Efficient coding

- Timing code running and looking at the output
- Common gotchas to speed things up
- Loops vs vectorization vs functional programming
    - Sorry Tom, I don’t mean let’s use Haskell
    - sapply 
    - purrr::map family and extensions
    - When loops are a good idea
- If you have to use a loop, then do this (e.g. pre-allocate a vector)
