What documentation exists for R?

Chapter 8: R Programming 91
8 R Programming
8.1 How should I write summary methods?
Suppose you want to provide a summary method for class "foo". Then summary.foo()
should not print anything, but return an object of class "summary.foo", and you should
write a method print.summary.foo() which nicely prints the summary information and
invisibly returns its object. This approach is preferred over having summary.foo() print
summary information and return something useful, as sometimes you need to grab something
computed by summary() inside a function or similar. In such cases you don’t want
anything printed.
8.2 How can I debug dynamically loaded code?
Roughly speaking, you need to start R inside the debugger, load the code, send an interrupt,
and then set the required breakpoints.
See section “Finding entry points in dynamically loaded code” in Writing R Extensions.
8.3 How can I inspect R objects when debugging?
The most convenient way is to call R_PV from the symbolic debugger.
See section “Inspecting R objects when debugging” in Writing R Extensions.
8.4 How can I change compilation flags?
Suppose you have C code file for dynloading into R, but you want to use R CMD SHLIB with
compilation flags other than the default ones (which were determined when R was built).
Starting with R 2.1.0, users can provide personal Makevars configuration files in
‘$HOME/.R’ to override the default flags. See section “Add-on packages” in R Installation
and Administration.
For earlier versions of R, you could change the file ‘$R_HOME/etc/Makeconf’ to reflect
your preferences, or (at least for systems using GNU Make) override them by the environment
variable MAKEFLAGS. See section “Creating shared objects” in Writing R Extensions.
8.5 How can I debug S4 methods?
Use the trace() function with argument signature= to add calls to the browser or any
other code to the method that will be dispatched for the corresponding signature. See
?trace for details.