Most common errors faced when programming with R

Question

I just wanted to know the most common errors encountered while working with R. I think it'll be very useful and will help me and others as well.

Answer 1

These the two most common errors I keep facing:

1. "could not find function" errors, usually caused by typos or not loading a required package
2. "Error in if" errors, caused by non-logical data or missing values passed to R's "if" conditional statement