Reproducing results from Cameroon & Trivadi book

Could you please share the code that you've run so far as a self-contained reprex (short for minimal reproducible example)? It will help us help you if we can be sure we're all working with/looking at the same stuff.

If you've never heard of a reprex before, you might want to start by reading the help page. The reprex dos and don'ts are also useful.