From: Achim Zeileis (zeileis@ci.tuwien.ac.at)
Date: Wed 15 May 2002 - 03:44:31 EST
Message-id: <3CE14CFF.FB62CEE7@ci.tuwien.ac.at>
"Vladimir N. Kutinsky" wrote:
>
> Hello,
>
> I faced something I can't understand. When I use boxplot.stats(1:10) and
> quantiles(1:10) the results are different for 25% and 75%:
>
> > boxplot.stats(1:10)
> $stats
> [1] 1.0 3.0 5.5 8.0 10.0
>
> > quantile(1:10)
> 0% 25% 50% 75% 100%
> 1.00 3.25 5.50 7.75 10.00
>
> Actually, I expected the value 3 for 25% and 8 for 75% as results of
> quantile(1:10). Can you please explain me why it isn't so.
The two ``hinges'' in boxplots are defined differently. They are
versions of the first and third quartile, but they are identical only
for odd n. This is explained in help(boxplot.stats)
Details:
The two ``hinges'' are versions of the first first and third
quartile, i.e. close to `quantile(x, c(1,3)/4)'. The hinges equal
the quartiles for odd n (where `n <- length(x)') and differ for
even n. Where the quartiles only equal observations for `n %% 4 ==
1' (n = 1 mod 4), the hinges do so additionally for `n %% 4 == 2'
(n = 2 mod 4), and are in the middle of two observations
otherwise.
> Regards,
> Vlad
>
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