[R] HELP: ff package

[BH]

I see now the configurations required for ffsave and ffload to work properly,
allowing the ff-package to do what it was designed to do:

1) file permanence
ff objects are stored in a temp directory and are deleted on exiting R. 
This is true of both standard and ff objects (so dont blame the package). 
In my case, I lost large and critical data files when exiting the program
because I didnt manage my temp directory and the options called fffinalize
and finonexit.  Use getOptions() to see your current setting for both of
these values.  Note: when you reassigning the temp directory to one you
establish, fffinalize changes automatically from delete to close.   

2) temp directory
ff files are physically stored in a temp directory and you want absolute
control over this location.  Create your own temp directory. I also see the
value of controlling the names of the files stored there.  Care here is
essential.  Package documentation points to use of fucntion pattern() to
control temp files.  Use it!  Otherwise, your temp file names are
exclusively random in nature.  More control is better, especially when
working with large dataframes (ffdf), which have many temp files associated
with them.  

3) rootpath
rootpath is an option for both ffsave and ffload.  The two must be
consistent with the temp directory you create.

4) External zip utility
Package documentation makes clear you need to use the external utilities zip
3.0 and unzip 6.0 from http://www.info-zip.org/.  Once installed,  adjust
the option(unzip="directory") to point to where the zip code is stored.
ffsave confirms the external code is working by showing how much compression
has been achieved in the value output.  

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