[R] boxplots

[Uwe Ligges]

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.


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


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

   [SNIP]

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

   [SNIP]

  }



So you can do for example:

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


Uwe Ligges

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