I believe boxplots uses "hinges" or "fourths" (the "letter values") instead
of quantiles. They could be very close, but not necessarily identical.
The definition of "fences" is
lower fence = lower hinge - k * H-spread
upper fence = upper hinge + k * H-spread
where H-spread = upper hinge - lower hinge, and k=1.5 for "inner" fences and
3 for "outer" fences. The hinges are the edges of the box in the boxplot.
I believe the boxplot uses inner fences.
HTH,
Andy
> -----Original Message-----
> From: Danni Wang [mailto:liuwang94710@hotmail.com]
> Sent: Friday, October 24, 2003 1:31 PM
> To: s-news@lists.biostat.wustl.edu
> Subject: [S] whiskers in boxplot - still confused
>
>
> Dear Group,
>
> There are some old discussions about how whiskers are drawn
> in boxplot( ). But it seems not answer my puzzle.
>
> According to the help file, whiskers are drawn to the nearest
> value not beyond a standard span from the quartiles, where
> the standard space is defined as 1.5(inter-quartiles).
>
> So, the whiskers cover a span of 1.5(inter-quartiles). My
> puzzle is from what quartiles, median, or others?
>
> Thanks.
>
> Danni
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