Sean Moriarity, please use your elixir knowledge to write a user defined function or a plugin in explorer. It's easy to attack other people and assume they are ignorant.
It has always been possible to do custom transformations via Series.transform. And here is a PR adding it to dataframes: https://github.com/elixir-explorer/explorer/pull/912 - the PR uses existing APIs, it was possible before, it just makes it more convenient. I am sure more will be added later