More on Spatial Data Analysis

that performs the macro expansion and then evaluates the expanded expression in the calling environment. At this point the function has no formal argument list and most of defmacro() is devoted to creating the correct formal argument list. Finally, as printing of functions in R actually uses the source attribute rather deparsing the function, we can make this print in a more user-friendly way. The last lines of defmacro() tell the function that its source code should be displayed as