problems with plot.formula

In R-1.8.1, I could work around the problem because the plot.formula
function is directly executable because it is exported from the graphics
package:

         _                   
platform sparc-sun-solaris2.8
arch     sparc               
os       solaris2.8          
system   sparc, solaris2.8   
status   Patched             
major    1                   
minor    8.1                 
year     2004                
month    02                  
day      05                  
language R

methods(plot)

[1] plot.HoltWinters*   plot.POSIXct        plot.POSIXlt       
 [4] plot.TukeyHSD       plot.acf*           plot.data.frame    
 [7] plot.decomposed.ts* plot.default        plot.dendrogram*   
[10] plot.density        plot.factor         plot.formula       
                                             ^^^^^^^^^^^^
[13] plot.function       plot.hclust*        plot.histogram     
[16] plot.isoreg*        plot.lm             plot.mlm           
[19] plot.ppr*           plot.prcomp*        plot.princomp*     
[22] plot.profile.nls*   plot.spec           plot.spec.coherency
[25] plot.spec.phase     plot.stl*           plot.table         
[28] plot.ts             plot.tskernel*     

    Non-visible functions are asterisked

plot.function
plot.function

function (x, from = 0, to = 1, xlim = NULL, ...) 
{
    if (!is.null(xlim)) {
...


While in R-1.9.x the plot.formula function is not exported:

version

_                   
platform sparc-sun-solaris2.8
arch     sparc               
os       solaris2.8          
system   sparc, solaris2.8   
status                       
major    1                   
minor    9.0                 
year     2004                
month    04                  
day      12                  
language R

methods(plot)

[1] plot.Date*          plot.HoltWinters*   plot.POSIXct*      
 [4] plot.POSIXlt*       plot.TukeyHSD       plot.acf*          
 [7] plot.data.frame*    plot.decomposed.ts* plot.default       
[10] plot.dendrogram*    plot.density        plot.ecdf          
[13] plot.factor*        plot.formula*       plot.hclust*       
[16] plot.histogram*     plot.isoreg*        plot.lm            
[19] plot.medpolish*     plot.mlm            plot.ppr*          
[22] plot.prcomp*        plot.princomp*      plot.profile.nls*  
[25] plot.spec           plot.spec.coherency plot.spec.phase    
[28] plot.stepfun        plot.stl*           plot.table*        
[31] plot.ts             plot.tskernel*     

    Non-visible functions are asterisked

plot.formula

Error: Object "plot.formula" not found

-----Original Message-----
From: r-devel-bounces@stat.math.ethz.ch
[mailto:r-devel-bounces@stat.math.ethz.ch]On Behalf Of Prof 
Brian Ripley
Sent: Tuesday, May 25, 2004 3:45 PM
To: Warnes, Gregory R
Cc: 'Troels Ring'; R-devel (E-mail)
Subject: Re: [Rd] problems with plot.formula


As this happens in exactly the same way in 1.8.1 and 1.9.0, 
why are you
blaming `recent changes in R 1.9.x'?  I am baffled as to what 
you think is
`recent'.

On Tue, 25 May 2004, Warnes, Gregory R wrote:

With the recent changes in R 1.9.x, it is now impossible to 

properly call

plot on a formula() where the formula is provided via a named first
argument.  On today's R-1.9.1-alpha:

x <- 1:10
y <- rnorm(x,0.25)

plot(x~y)

plot(x=x~y)

Error in terms.formula(formula, data = data) : 
	argument is not a valid model

plot(formula=x~y)

Error in plot(formula = x ~ y) : Argument "x" is missing, 

with no default

This occurs because plot.formula is no longer directly callable, 

It is, via graphics:::plot.formula.

No, actually it is not:

graphics::plot.formula

Error: 'plot.formula' is not an exported object from 'namespace:graphics'

and the
first argument to plot.formula() is 'formula' while the 

first argument to

plot() is 'x'.   Consequently one cannot properly pass a named first
argument since it will either fail for plot() or for 

plot.formula().  [I

suspect this is one reason why R CMD check complains about 

S3 methods that

don't match the call of the base method.]

This is much of a problem in interactive use, but it does 

cause problems in

functions, like my gregmisc::overplot(), which use the 

standard idiom

    m <- match.call()
    m[[1]] <- as.name('plot')
    eval(m, parent.frame() )

Not a standard idiom for a generic with a formula method, and 
I think you 
really should be dispatching to the method here.

The problem is that plot.formula is not exported, so I cannot dispatch
directly to it.  (This is what I did previously).

-Greg

[...]

-- 
Brian D. Ripley,                  ripley@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

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