[Rd] Bug in stats::plot.hclust/graphics:::plotHclust/underlying C code (C_dend) in R-3.0?

[Martin Maechler]

>>>>> Peter Langfelder <peter.langfelder at gmail.com>
>>>>>     on Fri, 31 May 2013 16:32:06 -0700 writes:

    > Hi all, it appears that plot.hclust disregards the
    > argument 'cex'. Up until 2.15.1 (and probably all 2.15.x),
    > specifying cex in plot.hclust changed the size of the
    > plotted labels on each leaf. In 3.0.0 the character size
    > remains the same irrespective of the cex setting. Since
    > the help text for plot.hclust does not mention the cex
    > argument, it is possible that an "undocumentde feature"
    > was simply removed - but it was very useful when it was
    > available.

    > The following code illustrates the problem:

>    data = c(1:20)
>    dst = dist(data)
>    tree = hclust(dst, method = "a")
>    plot(tree, cex = 1)
>    plot(tree, cex = 0.5)
>    plot(tree, cex = 0.2)


    > Under R-2.15 and earlier, the leaf labels would get
    > progressively smaller; under 3.0.0, the label size remains
    > the same. I tried this both under Windows

    > R version 2.15.1 (2012-06-22) 

 [............]
    

    > R version 3.0.0 (2013-04-03)

 [............]


    > and under Linux

    > R version 3.0.0 Patched

[...........]

    > Looking at the source code of plot.hclust leads to
    > graphics:::plotHclust which calls .External.graphics,
    > which is where my ability to read code quickly stops :)

    > I realize that these are not the most recent releases but
    > I couldn't find anything mentioning a bug fix for this in
    > the changelog, so I assume it has not been fixed.

You are right.    Duncan Murdoch found the place (in the C code
indeed), and I've found and fixed the small inconsistency that
happened (between 2.15.x  and 3.0.0) when that code was slightly
streamlined and moved to the 'graphics' package.

    > Thanks,
    > Peter

Thank you Peter,  for reporting it in such a precise manner!

Martin Maechler, ETH Zurich