NaN, Inf to NA

Sat, May 28, 2011 8:33 AM

On 27/05/2011 11:52 AM, Marc Schwartz wrote:

On May 27, 2011, at 10:33 AM, Duncan Murdoch wrote:

On 27/05/2011 11:11 AM, Martin Maechler wrote:

  Duncan Murdoch<murdoch.duncan at gmail.com>
      on Fri, 27 May 2011 08:23:14 -0400 writes:

     >   On 11-05-27 4:27 AM, Albert-Jan Roskam wrote:

     >>   Aha! Thank you very much for that clarification! It would
     >>   be much more user friendly if R generated a
     >>   NotImplementedError or something similar. The 'garbage
     >>   results' are pretty misleading, esp. to a novice.

     >   I think that's a good idea.  The default methods are
     >   documented to work on atomic vectors; dataframes are not
     >   atomic vectors, so it would be reasonable to generate an
     >   error.  (See ?is.atomic for a definition of atomic
     >   vectors.)

     >   I'll see if this causes a lot of trouble...

     >   Duncan Murdoch

Duncan,
do you remember the issue of mean(), var(), median(),... etc
that was the topic a few weeks ago ?

I strongly advocated that  mean.data.frame() should become
*deprecated*, and I would propose the same for the functions
mentioned here.

I think you may have misunderstood my proposal.  Currently is.nan, is.finite and is.infinite have no data.frame methods, so the default method is used.  The problem is that the default method is too permissive:  it operates on the data.frame by treating it as a list; then it returns FALSE for each list element.  (If there is only one row, it applies the test to the singleton in the column.)   This is pretty strange default behaviour.

What I'm proposing is that the default method should trigger an error if you try to send it anything that's not atomic.  This gives sensible behaviour in most cases; the only one where it doesn't work is a list of singletons, which used to be handled sensibly, but will now fail.

(There's still a question about what the answer should be for these functions when applied to character or raw vectors, which are both atomic.  I'm leaning towards returning FALSE for every element, which matches the current behaviour, but perhaps those should also generate an error.)

I think this partially addresses Bill's objection, but not completely.  Someone could still put a class on an atomic vector, and that might not be handled properly by the default method.

People should  *apply (or *ply) on data frames, and not expect
that all kind of functions have data.frame methods
which are simply equivalent to basically  sapply(<df>,<function>)

{and yes -- all this belongs to R-devel rather than R-help}

Where I've moved it now.

Duncan Murdoch

Martin


I snipped some of the older content and added Bill.

It seems to me that unless the 'x' argument is both atomic and numeric, these functions really don't have much utility, if you are going to implement standard default behavior and more rigorous error checking.

In the commit yesterday I signalled an error for character or raw vector 
input, and this caused about 30 packages to fail testing.  I checked a 
couple of them, and they both had applied one of the functions to 
character data.  Before introducing the error, these tests were 
basically harmless.

One example had code like this:

stop.na.inf <- function(x) {
   if(any(is.na(x)) | any(is.infinite(x)))
         stop("Either an NA or an infinite in the data: ",
              deparse(substitute(x)), ".\n",
              "   Eliminate those values or use imputation")
}

This little utility function was used a lot, including on character 
data.  Since it is rather ugly to say which types are okay to pass, I've 
reverted that part of the change and am running new tests, I will commit 
soon.

(The test could be improved a little; I'll send advice to the author on 
that.  But I don't think we should require x not to be a character vector.)

Duncan Murdoch

NaN, Inf to NA

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