See virtualstaticvoid/heroku-buildpack-r#113
heroku create --stack heroku-16
heroku buildpacks:add https://github.com/heroku/heroku-buildpack-python.git
heroku buildpacks:add https://github.com/virtualstaticvoid/heroku-buildpack-r.git#heroku-16
git push heroku master
heroku run R --no-save -f /app/test.R
heroku run python /app/test.py