[Rd] plot ignores type= "n" when x is factor (PR#13703)

[Prof Brian Ripley]

On Thu, 14 May 2009, pauljohn at ku.edu wrote:

> Full_Name: Paul E. Johnson
> Version: 2.9.1

Where did you get that?  Time travel?

> OS: Linux (Ubuntu 9.04)
> Submission from: (NULL) (129.237.61.25)
>
>
> x <- gl(2,50)
> y <- rnorm(100)
> plot(x,y)
> plot(x,y, type="n")
>
>
> I *wish* the last one would draw a blank plot box w/axes, but it does not. It
> fills in the middle with a box plot. I've not seen this problem when x is
> numeric.

Because this is a call to the 'factor' (see ?plot.factor).  Although 
?plot says

      ...: Arguments to be passed to methods, such as graphical
           parameters (see 'par'). Many methods will accept the
           following arguments:

           'type' what type of plot should be drawn.  Possible types are

'many' does not mean 'all' and all the other values of 'type' would be 
inappropriate for plot.factor.  Note that plot.factor is a wrapper for 
a call to barplot(), spineplot() or (in your case) boxplot(), which do 
not take a 'type' argument.

If plot.factor() or barplot() or boxplot() allowed a 'type' argument, 
what value would be appropriate to give the usual plot?  Not as far as 
I can see any of those listed in ?plot, and that says all other values 
are errors.


So, this is not a bug, it was not marked for the wishlist (see the R 
FAQ), and there seems no simple way to accommodate the implicit wish.

-- 
Brian D. Ripley,                  ripley at stats.ox.ac.uk
Professor of Applied Statistics,  http://www.stats.ox.ac.uk/~ripley/
University of Oxford,             Tel:  +44 1865 272861 (self)
1 South Parks Road,                     +44 1865 272866 (PA)
Oxford OX1 3TG, UK                Fax:  +44 1865 272595