Source code analysis for R ?

A GUI-heavy R project of mine has mushroomed into well over 1000 lines of
code. It is getting to a point where I am wondering if someone had something
like a script to summarize which functions call which other etc.  

Note that I am not looking at profiling but rather a (static) analysis of
code interdepence.  Does anybody here have anything for this task?

Thanks for any pointers,  Dirk

Don't drink and derive. Alcohol and analysis don't mix.