I've been using ggmap::geocode() for turning addresses into geocodes but datasciencetoolkit.org no longer supports this feature and Google now only allows one geocode request for free per day.
Google now allows unlimited geocode requests per day. I ran about 1000 yesterday. You can also use the census website to geocode. You may want to read my blog entry on geocoding, http://adelieresources.com/2019/01/comparing-free-geocoding-engines/ , I use google but it has some potential gotcha issues.
If you would like my code for accessing the census geocoder, let me know. Someday I plan to clean it up for release.