31.1 Executive Summary: What to usually do

When you’re editing one PEcAn package and want to use a function from any other R package (including other PEcAn packages), the standard method is to add the other package to the Imports: field of your DESCRIPTION file, spell the function in fully namespaced form (pkg::function()) everywhere you call it, and be done. There are a few cases where this isn’t enough, but they’re rarer than you think. The rest of this section mostly deals with the exceptions to this rule and why not to use them when they can be avoided.