Ask anyone how much time has elapsed since September last year and they’ll probably start counting on their fingers: “October, November…” and tell you “just over 9 months.”
So, when faced as I was today with a data frame (named dates) like this:
pmid1 year1 month1 pmid2 year2 month2 21355427 2010 Dec 21542215 2011 Mar 21323727 2011 Feb 21521365 2011 Jun 21297532 2011 Feb 21336080 2011 Mar 21291296 2011 Apr 21591868 2011 Jun ...
How to add a 7th column, with the number of months between “year1/month1” and “year2/month2”?
Read the rest…