Here's a simple example:
setClass("foo", contains="numeric")
x <- new("foo", 4)
# Division by scalar works
> x / 2
An object of class "foo"
[1] 2
# Division by array blows up
y <- array(2, c(2, 2))
> x / y
Error in getDataPart(c(2, 2, 2, 2)) : node stack overflow
# Not sure I understand the error message, but in any case, based on
the success of ...
> x / as.numeric(y)
[1] 2 2 2 2
# ... wrote a division method for arrays, which worked.
> setMethod("/", signature = c("foo", "array"), function(e1, e2) e1 /
> as.numeric(e2))
[1] "/"
> x / y
[1] 2 2 2 2
Is it always necessary to define "array" methods for arithmetic on
user defined classes? Maybe the answer has to do with the error
message I did not understand.
Thanks,
Dan Murphy
> sessionInfo()
R version 3.1.0 (2014-04-10)
Platform: x86_64-w64-mingw32/x64 (64-bit)
locale:
[1] LC_COLLATE=English_United States.1252 LC_CTYPE=English_United
States.1252 LC_MONETARY=English_United States.1252 LC_NUMERIC=C
LC_TIME=English_United States.1252
attached base packages:
[1] stats graphics grDevices utils datasets methods base
loaded via a namespace (and not attached):
[1] tools_3.1.0
>
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