On 07/07/2019 11:49 a.m., Ghiggi Gionata wrote:
Hi all !
I noticed a strange behaviour of the function `class<-` when a class-specific
'[[.' method is defined.
Here below a reproducible example :
#-------------------------------------------------------------------.
counttt <- 0
`[[.MYCLASS` = function(x, ...) {
counttt <<- counttt + 1
# browser()
x = NextMethod()
return(x)
}
df <- as.data.frame(matrix(1:20, nrow=5))
class(df) <- c("MYCLASS","data.frame")
counttt
# The same occurs when using structure(, class=) or attr(,"class")<-
df <- as.data.frame(matrix(1:20, nrow=5))
df <- structure(df, class=c("MYCLASS","data.frame"))
attr(df, "class") <- c("MYCLASS","data.frame")
#-------------------------------------------------------------------.
Why in this example `class<-` is calling `[[.MYCLASS` 9 times ?
Is there a way to avoid `class<-` to call `[[.MYCLASS` ?
Thank you in advance for your help and suggestions.
This is what I see:
> counttt <- 0
>
> `[[.MYCLASS` = function(x, ...) {
+ counttt <<- counttt + 1
+ # browser()
+ x = NextMethod()
+ return(x)
+ }
>
> df <- as.data.frame(matrix(1:20, nrow=5))
> class(df) <- c("MYCLASS","data.frame")
> counttt
[1] 0
So there's something else going on in your system. Maybe post
sessionInfo()?
Duncan Murdoch
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