This showcase demonstrates how to create dictionaries computationally in R, covering synonym finding, semantic similarity measures, and the automatic generation of dictionary entries from corpus data. It is aimed at researchers in lexicography, computational linguistics, and digital humanities who want to apply corpus and semantic methods to dictionary creation. This tutorial is part of the Language Technology and Data Analysis Laboratory (LADAL), a free, open-access research infrastructure at the University of Queensland. LADAL provides tutorials, tools, and courses for researchers working with language data. All materials are freely available at https://ladal.edu.au and are part of the Language Data Commons of Australia (LDaCA), funded by ARDC and NCRIS.