Many thanks to those who answered my question about how to test
for the existence of a file: Berwin Turlach, Jari Oksanen, Henrik
Bengtsson, Uwe Ligges, and Joerg Maeder.
The simplest solution is to use the built-in (!!!) function
file.exists() which returns TRUE if the file exists, and FALSE
if it doesn't. Like, duhhhhhh!!! It's exactly what I wanted.
Special thanks to Berwin Turlach who explained to me how I might
have found out about file.exists() for my own self ---
> 1.) In R type help.start().
> 2.) Go to browser and select "Search Engine & Keywords".
> 3.) Enter "file" as search keyword and press the search button
> 4.) Peruse the list of hits until something suitable comes up
A couple of suggestions to the developers:
1) It would nice for us bunnies if, say, help.search() made
a suggestion to do Berwin's four steps if help.search()
itself turns up nothing useful.
2) The ``See also'' for file.access et al. should include
``files'' which contains the documentation on a whole
elephantful of useful functions. The item ``files'' comes
last in the items of the list turned up by the search wherein
the word ``file'' actually appears in the link. The faint
of heart might well become discouraged before getting there.
I also think that an explicit link from file.access to
file.exists (the two are closely related) would be helpful.
Thanks again to all my enlighteners.
cheers,
Rolf Turner
rolf at math.unb.ca
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