Add a Horizontal Boxplot to the Current Plot
p.hboxp(x, y.lo, y.hi, boxcol = 3,
        medcol = 2, medlwd = 5, whisklty = 2, staplelty = 1)x | 
 univariate data set.  | 
y.lo, y.hi | 
 minimal and maximal user coordinates
or   | 
boxcol, medcol | 
 color of the box and the median line.  | 
medlwd | 
 line width of median line.  | 
whisklty, staplelty | 
 line types of the whisker and the staple, the latter being used for the outmost non-outliers.  | 
....
Martin Maechler building on code from Markus and Christian Keller.
boxplot(**, horizontal = TRUE, add= TRUE).
## ==> See code in 'histBxp' (.) and example(histBxp) ! ##
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