[R] boxplots -- new argument for location

[Martin Maechler]

>>>>> "Uwe" == Uwe Ligges <ligges at statistik.uni-dortmund.de> writes:
(on Sun, 27 May)

    Uwe> Roger Koenker wrote:

    >> Was there ever a convenient method provided to add boxplots to the
    >> current plot at specified x values?  There was a question by Martin
    >> Maechler some time ago here, but I could seem to find any
    >> satisfactory resolution of it.

    >> I see that there is an add=T option to boxplot and bxp, but I don't
    >> see how to set the x-values.


    Uwe> bxp() can easily be extended to handle a new argument like
    Uwe>  x.loc = NULL , in which you can specify the x-values manually:

(see below)
Thank you, Uwe,  a feature long overdue.
I'd propose to call the new argument `at' instead of `x.loc' 
since it's similar to the one in axis() and
since it will be `y locations' when horizontal = TRUE
-- and I'd add the `at =' both to boxplot() and to bxp() .

 Uwe> bxp <- 
 Uwe> function (z, notch = FALSE, width = NULL, varwidth=FALSE, notch.frac=0.5, 
 Uwe> boxwex = 0.8, border = par("fg"), col = NULL, log = "", pars = NULL, 
Uwe> -    frame.plot = axes, horizontal = FALSE, add = FALSE, ...) 
Uwe> +    frame.plot = axes, horizontal = FALSE, add = FALSE, x.loc = NULL,
 Uwe> ...) 
 Uwe> {

    Uwe> [SNIP]

 Uwe>   if (!add) {
 Uwe>     plot.new()
 Uwe>     if (horizontal) 
 Uwe>       plot.window(ylim = c(0.5, n + 0.5), xlim = ylim, 
 Uwe>         log = log)
 Uwe>     else plot.window(xlim = c(0.5, n + 0.5), ylim = ylim, 
 Uwe>         log = log)
 Uwe>   }
 Uwe> + if(is.null(x.loc))
 Uwe> +        x.loc <- 1:n
 Uwe> - for (i in 1:n) bplt(i, wid = width[i], stats = z$stats[, 
 Uwe> + for (i in 1:n) bplt(x.loc[i], wid = width[i], stats = z$stats[, 
 Uwe>     i], out = z$out[z$group == i], conf = z$conf[, i], notch = notch, 
 Uwe>     border = border[(i - 1)%%length(border) + 1], col = if (is.null(col)) 
 Uwe>       col
 Uwe>       else col[(i - 1)%%length(col) + 1], horizontal = horizontal)
 Uwe> 
 Uwe>    [SNIP]
 Uwe> 
 Uwe>   }

    Uwe> So you can do for example:

    Uwe>  my.bxp <- boxplot(data.frame(v13 = 1:10, v15 = 2:11))
    Uwe>  plot(1:20) 
    Uwe>  bxp(my.bxp, add = TRUE, x.loc = c(13, 15))

Any proposal for a more interesting example (to be added to the on-line
help in ?boxplot or ?bxp -- ?

Martin Maechler <maechler at stat.math.ethz.ch>	http://stat.ethz.ch/~maechler/
Seminar fuer Statistik, ETH-Zentrum  LEO D10	Leonhardstr. 27
ETH (Federal Inst. Technology)	8092 Zurich	SWITZERLAND
phone: x-41-1-632-3408		fax: ...-1228			<><
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