The default initialization for slots of class "factor" and
"data.frame" gives NULL. This seems odd, since those slots can't ever
be set to NULL by the user. I would expect zero-length instances of
factor and data.frame.
Here is an example:
setClass("FOO", representation(a="factor", b="data.frame", c="numeric"))
[1] "FOO"
> ff <- new("FOO")
> ff
An object of class "FOO"
Slot "a":
NULL
Slot "b":
NULL
Slot "c":
numeric(0)
sessionInfo()
R version 2.3.0, 2005-12-26, powerpc-apple-darwin8.3.0
attached base packages:
[1] "tools" "methods" "stats" "graphics" "grDevices" "utils"
[7] "datasets" "base"
Slot c is initialized as I was expecting.
+ seth
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