Have lubridate subtraction return only a numeric value

Question

I have one variable called Started which is the date on which human subjects enrolled in a study and another variable called dos1 which is the date

Answer 1

That's definitely a bug in lubridate. I've made an error report and will fix it for version 0.1:

http://github.com/hadley/lubridate/issues#issue/75

Thanks for bringing it to my attention.