graphics::Axis loosing S3/S4 class attributes of 'x' in 2.7.0 RC

-----Original Message-----
From: Duncan Murdoch [mailto:murdoch at stats.uwo.ca] 
Sent: 22 April 2008 13:01
To: Sklyar, Oleg (MI London)
Cc: R-devel at r-project.org
Subject: Re: [Rd] graphics::Axis loosing S3/S4 class 
attributes of 'x' in 2.7.0 RC

On 22/04/2008 7:25 AM, Sklyar, Oleg (MI London) wrote:

Following my previous post on S3 method despatch, I put 

debug messages 

in the code of Axis, Axis.default and plot.default in 
graphics/R/axis.R and graphics/R/plot.R to print the class of x, at 
and y on plot. After recompiling R, what I see is that x *lost* its 
class attribute (at least for classes not known to 'graphics') in 
Axis, called directly from plot.default and this could be 

the reason 

why R did not despatch on Axis.MyClass from my previous post. This 
happens for both S3 and S4 classes as in the code below! 

Funny enough, 

even "integer" was reset to numeric in Axis...

If you look at plot.default, you'll see it passes x and y 
through xy.coords to get coordinates.  That function ends with

return(list(x=as.double(x), y=as.double(y), xlab=xlab, ylab=ylab))

so that's where classes get removed.  If you don't want this 
to happen, shouldn't you be defining plot.MyClass, or calling 
the default with axes=F, and then calling Axis on your object 
yourself?

Is this really an intended behaviour? It looks very wrong to me!

This is documented:  ?plot.default tells you to look at 
?xy.coords for details of how x and y are handled, and 
xy.coords says "In any other case, the 'x' argument is 
coerced to a vector and
      returned as *y* component where the resulting 'x' is just the
      index vector '1:n'.  In this case, the resulting 'xlab' 
component
      is set to '"Index"'."

Duncan Murdoch

Thanks,
Oleg

*** R version 2.7.0 RC (2008-04-20 r45403) 

[/research/osklyar/R-devel]

***

Axis

function (x = NULL, at = NULL, ..., side, labels = NULL) {
    cat("In Axis() class(x)=", class(x), "; class(at)=", class(at),
        "\n", sep = "")
    if (!is.null(x))
        UseMethod("Axis", x)
    else if (!is.null(at))
        UseMethod("Axis", at)
    else axis(side = side, at = at, labels = labels, ...) }
<environment: namespace:graphics>

graphics:::Axis.default

function (x = NULL, at = NULL, ..., side, labels = NULL) {
    cat("In Axis.default() class(x)=", class(x), "; class(at)=",
        class(at), "\n", sep = "")
    if (is.null(at) && !is.null(x))
        at = pretty(x)
    axis(side = side, at = at, labels = labels, ...) }
<environment: namespace:graphics>

setClass("MyClass", representation(smth="character"),

contains="numeric")
[1] "MyClass"

a = new("MyClass", runif(10))
a

An object of class "MyClass"
 [1] 0.773237167 0.548630205 0.987956687 0.212667925 0.337135151
0.112210501
 [7] 0.007140895 0.972028903 0.443581963 0.536452424 Slot "smth":
character(0)

plot(1:10,a)

In plot.default() class(x)=integer; class(y)=MyClass In Axis() 
class(x)=numeric; class(at)=NULL In Axis.default() 

class(x)=numeric; 

class(at)=NULL In Axis() class(x)=numeric; class(at)=NULL In 
Axis.default() class(x)=numeric; class(at)=NULL

plot(a,1:10)

In plot.default() class(x)=MyClass; class(y)=integer In Axis() 
class(x)=numeric; class(at)=NULL In Axis.default() 

class(x)=numeric; 

class(at)=NULL In Axis() class(x)=numeric; class(at)=NULL In 
Axis.default() class(x)=numeric; class(at)=NULL

b = runif(10)
class(b)="AnotherClass"
plot(b,1:10)

In plot.default() class(x)=AnotherClass; class(y)=integer In Axis() 
class(x)=numeric; class(at)=NULL In Axis.default() 

class(x)=numeric; 

class(at)=NULL In Axis() class(x)=numeric; class(at)=NULL In 
Axis.default() class(x)=numeric; class(at)=NULL

plot(1:10)

In plot.default() class(x)=integer; class(y)=NULL In Axis() 
class(x)=numeric; class(at)=NULL In Axis.default() 

class(x)=numeric; 

class(at)=NULL In Axis() class(x)=numeric; class(at)=NULL In 
Axis.default() class(x)=numeric; class(at)=NULL>

sessionInfo()

R version 2.7.0 RC (2008-04-20 r45403) x86_64-unknown-linux-gnu

locale:

LC_CTYPE=en_GB.UTF-8;LC_NUMERIC=C;LC_TIME=en_GB.UTF-8;LC_COLLATE=C;LC_

MO 

NETARY=C;LC_MESSAGES=en_GB.UTF-8;LC_PAPER=en_GB.UTF-8;LC_NAME=C;LC_ADD

RE 

SS=C;LC_TELEPHONE=C;LC_MEASUREMENT=en_GB.UTF-8;LC_IDENTIFICATION=C

attached base packages:
[1] stats     graphics  grDevices utils     datasets  methods   base


Dr Oleg Sklyar
Technology Group
Man Investments Ltd
+44 (0)20 7144 3803
osklyar at maninvestments.com

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