[Rd] Mosaicplot coloring (PR#8537)

[Achim Zeileis]

On Sun, 29 Jan 2006 greg.kochanski at phon.ox.ac.uk wrote:

> Full_Name: Greg Kochanski
> Version: 2.2.1
> OS: Debian Linux (testing)
> Submission from: (NULL) (212.159.16.190)
>
>
> mosaicplot(x, shade=TRUE) is intended to color the blocks
> blue if they are more common than one might expect
> and red if they are rarer than one might expect.
>
> Unfortunately, if a block is much rarer than expected,
> it is so narrow that one cannot see the red.

Where is the bug?? Please read Section 9 in
  http://CRAN.R-project.org/doc/manuals/R-FAQ.html
and also the posting guide at
  http://www.R-project.org/posting-guide.html

> Thus,
> a casual inspection of the mosaicplot will miss some
> of the most statistically significant results.

Note that with this shading you are using colored cells and statistically
significant results might not coincide.

> This is partially an intrinsic problem and cannot be
> entirely fixed, but it is made worse by the black outlines
> around each block.    Blocks with very small probabilities
> show as black, not red.   The broken outlines on the
> red blocks help, but not quite enough.
>
> I would suggest that there be an option to either turn off
> the black outlines when for the colored blocks,
> or an option to use colored outlines.

For an enhanced implementation of mosaic plots written in the grid
graphics system, see the package "vcd" and the functions mosaic() and
strucplot(). See the package vignettes for details on control of the
graphical appearance and also for combining shading and significance
testing. To overcome the problem of small cells, another approach is to
plot expected instead of observed frequencies.
Z

> If those options are somehow hidden in the ... part of the
> argument list for mosaicplot(), I apologize, but then this
> bug report should be converted to a documentation bug.
> Nowhere in help(mosaicplot) does it say what one can put into
> the unspecified arguments (...).
>
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