wishlist -- Fix for major format.pval limitation (PR#9574)

On 3/20/2007 1:40 PM, Gabor Grothendieck wrote:

On 3/20/07, Duncan Murdoch <murdoch at stats.uwo.ca> wrote:

On 3/20/2007 12:44 PM, Gabor Grothendieck wrote:

On 3/20/07, murdoch at stats.uwo.ca <murdoch at stats.uwo.ca> wrote:

On 3/20/2007 11:19 AM, charles.dupont at vanderbilt.edu wrote:

Full_Name: Charles Dupont
Version: 2.4.1
OS: linux 2.6.18
Submission from: (NULL) (160.129.129.136)


'format.pval' has a major limitation in its implementation. For example
suppose a person had a vector like 'a' and the error being ?0.001.

    > a <- c(0.1, 0.3, 0.4, 0.5, 0.3, 0.0001)
    > format.pval(a, eps=0.01)

If that person wants to have the 'format.pval' output with 2 digits always
showing (like passing nsmall=2 to 'format'). That output would look like
this.

    [1] "0.10"   "0.30"   "0.40"   "0.50"   "0.30"   "<0.01"

That output is currently impossible because format.pval can only
produce output like this.

    [1] "0.1"    "0.3"    "0.4"    "0.5"    "0.3"    "<0.01"


---------------------------------------------------------------
a <- c(0.1, 0.3, 0.4, 0.5, 0.3, 0.0001)
format.pval(a, eps=0.01)

But there's a very easy workaround:

format.pval(c(0.12, a), eps=0.01)[-1]

gives you what you want (because the 0.12 forces two decimal place
display on all values, and then the [-1] removes it).

Clever, but the problem would be that summary.lm, etc. call format.pval so the
user does not have a chance to do that.

I don't see how this is relevant.  summary.lm doesn't let you pass a new
eps value either.  Adding an "nsmall=2" argument to format.pval wouldn't
help with the display in summary.lm.

I suppose we could track down every use of format.pval in every function
in every package and add nsmall and eps as arguments to each of them,
but that's just ridiculous.  People should accept the fact that R
doesn't produce publication quality text, it just provides you with ways
to produce that yourself.

Duncan Murdoch

You are right in terms of my example which was not applicable but I
think in general that format.pval is used from within other routines rather than
directly by the user so the user may not have a chance to massage it
directly.

Right, but this means that it is more or less useless to change the
argument list for format.pvals in the way Charles suggested, because all
of the existing uses of it would ignore the new parameters.

It would not be so difficult to change the behaviour of format.pvals so
that for example "digits=2" implied the equivalent of "nsmall=2", but I
don't think that's a universally desirable change.

The difficulty here is that different people have different tastes for
presentation-quality text.  Not everyone would agree that the version
with trailing zeros is preferable to the one without.  R should be
flexible enough to allow people to customize their displays, but not
necessarily by having every print method flexible enough to satisfy
every user:  sometimes users need to construct their own output formats.

Duncan Murdoch