Re: [Rd] digits in summary.default

From: Martin Maechler <maechler_at_stat.math.ethz.ch>
Date: Fri 15 Sep 2006 - 07:52:14 GMT

>>>>> "Simone" == Simone Giannerini <sgiannerini@gmail.com> >>>>> on Thu, 14 Sep 2006 11:14:51 +0200 writes:

    Simone> Dear all, the number of significant digits in     Simone> summary default is

    Simone> digits = max(3, getOption("digits") - 3)

    Simone> on my platform this results to be 4. The point is
    Simone> that if you have, say, integer data of magnitude
    Simone> greater than 10^3 the command summary will produce
    Simone> heavily rounded results.

    Simone> A simple example follow:

>> x <- c(123456,234567,345678)

>> x

    Simone> [1] 123456 234567 345678

>> summary(x)

    Simone> Min. 1st Qu. Median Mean 3rd Qu. Max. 123500     Simone> 179000 234600 234600 290100 345700

    Simone> # quite different from

>> quantile(x)

    Simone> 0% 25% 50% 75% 100%     Simone> 123456.0 179011.5 234567.0 290122.5 345678.0             

Yes, a very very very old topic, and has been frequently on the R lists.
The reason for this default has been compatibility with S and in particular Splus-3.4 (1996) which used to be a partial role model for R in its infancy.

However, I now see that Insightful also must have decided that the old S setting was not satisfactory and that one can and should do better.

    Simone> Is it possible to adapt the number of significant
    Simone> digits to the magnitude of the data?  The first
    Simone> thing that comes into my mind is 

    Simone>      digits = nchar(trunc(max(x))) #

that's a first step of one thing to consider, yes, but does need quite a bit of fixup before it's usable.

Since I've now seen the code of summary.default in S-plus 6.2, I'm not in a good position to propose a code change here --- unless Insightful ``donates'' their 3 lines of implementation to R {which I think would be quite fair given the recent flurry of

    things they've recently ported into S-plus 8.x}

    Simone> If it is not possible then I think it would be nice     Simone> to mention the issue in the documentation.

The issue is mentioned but maybe in a too terse way.

I agree that I'd also want to change this behavior. It's definitely too late for R 2.4.0, since although this may seem like a small thing to do,
it can have quite a large effect in many outputs of R scripts.

    Simone> Thanks for the attention,

    Simone> Simone

>> R.version

    ..............
    (does not really matter - here for once)

Martin Maechler, ETH Zurich



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