![Looping versus LOC-ing revisited](https://blogs.sas.com/content/iml/files/2011/08/posrowtiming.png)
In a previous post, I discussed how to use the LOC function to eliminate loops over observations. Dale McLerran chimed in to remind me that another way to improve efficiency is to use subscript reduction operators. I ended my previous post by issuing a challenge: can you write an efficient