I just spent about an hour bug-tracking.  I had expected the following to
throw an error:

  d <- data.frame( x=1:5, y=6:10 )
  valid <- c(TRUE, FALSE)
  d[valid,]

I understand that R recycles "when fit," but I had not expected it to
recycle, then truncate, and not give even a warning.  maybe there is a good
reason for this.

I would love to be able to teach R to my MFE students.  alas, I don't feel
that I can inflict on them the mysterious errors in R.  this ranges from
poor checking of when variables exist to auto-recycling (without an ability
to turn this off even with an option) to the non-printing of the last
numbered R source code statement upon an error (that I can see in the
traceback()) to non-expected behavior (e.g., subset(d,x,select=-c("a",
"b"))) to .  I know many of these issues can be fixed and/or do not bother
the experts, and I am personally happy to live with R for its power despite
its drawbacks; but IMHO it is just too much to ask from a set of bewildered
novice master students.

I hope the R team will at some point in the future pick up on making the
core language less mysterious upon setting an option, at least in "user
space".

/iaw

----
Ivo Welch (ivo.welch@gmail.com)

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