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

[hadley wickham]

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

It would be interesting to take a similar approach to grid - return a
table object which could then be tweaked as necessary, rather than
having to build everything up from scratch.  A very big job though!

Hadley