[R] Change in behavior of compare statement

From: Tomas Andersson <tomasan_at_gmail.com>
Date: Tue 20 Sep 2005 - 02:25:15 EST


Dear all,

I have come across some Windows Script code which calls the "file.exists" function in R to check for the existence of a particular file on an R server. This is what the code looks like:

            do
            {
                        // some useful code
            }
            while (m_workspace.session.eval("file.exists(" + dataFile
+ ")") != "1");

It appears that the behavior of this code is different when used with R version 2.1.1 compared to R version 1.9.1. If the compare statement s is changed from

            while (s != "1")
to

            while (s != "True")
or

            while !(s)

the behavior of the code is the same with both versions of R.

After reading the R documentation, I have not found any evidence that the original syntax (s != "1") is in any way recommended or supported (in version 2.1.1). Still, my questions are:

  1. Is it possible that the syntax has been supported in older versions of R?
  2. Is the reason for the recent change in behavior known and documented anywhere?

I have been unable to find an answer to either question, so any information about this would be appreciated.

Thanks,

T. Andersson



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