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

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...

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

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_ADDRE
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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