Thanks for creating this. I posted the case study on our web site with the author “Aravind S” as that’s the most specific name you provided. It does link to your GitHub, but that’s not any more specific about your identity.
Copyright is about quality, not quantity. As soon as you modify the original (for instance, changing “R” to “Python”), you have created a derived work, whose copyright is immediately assigned to you (you don’t need to file anything or even write "copyright on it—it’s automatically assigned to you through the act of creating the derived work).
Now, in order for someone else to use your intellectual property legally, you need to provide a license.
Now, if it’s a derived work, that doesn’t necessarily give you the right to distribute it or license it to others for use—you can’t change a word of a copyrighted novel released under a proprietary license (for instance, through printing a book) and then redistribute the novel as your own work. But in this case, the original was CC-BY, so you can legally redistribute your derived work.
I’m going to assume that your intent was to assign your copyright for the derived work to to me, as that’s what you wrote. If that was not your intent, or if you could do me the favor of adding a surname, please create a pull request for a new version on our web site (under stan-dev organization).