[Rd] manage R function and data dependencies like 'make'

[Lutz Prechelt]

Dear R-devels,

I am looking for a package (or some other infrastructure) for the
following situation:

I am doing a larger data evaluation.
I have several dozen data files and do not want to keep the persistent
data in the R workspace (for robustness reasons).
I have several dozen R files, some for reading and preprocessing data
files, others for doing plots or analyses.
I will make frequent changes to both data files and R files while doing
the analysis.

I would like to automate mechanisms that allow 
- a data file reading function to suppress its actual work if neither
the data file nor the R file containing the function were modified since
the data file was last read
- an R file sourcing function to suppress its actual work if the R file
has not been modified
- and perhaps even: automate re-reading a data file upon access to the
corresponding dataframe iff the file has been modified since the
dataframe was created.

In short: Something like Unix's 'make', but for managing dependencies of
functions and dataframes in addition to files. In R. (And of course I am
very open for solutions that are more elegant than what I have sketched
above.)

I could not find something in the help and have rather few ideas for
good search terms.

I any such thing available?
(If no such infrastructure exists, what is the right R function for
accessing file modification dates?)

Thanks!

  Lutz