On 09/11/13 09:16, peter dalgaard wrote:
On Sep 10, 2013, at 22:56 , Rolf Turner wrote:
On 09/11/13 07:54, Davis, Brian wrote:
I'm sure this has been answered before but alas my googlefoo is not that strong.
I have several .Rdata files with a single object in them. I need to set the class of the
object to "myClass". Unfortunately, I don't know the name of the object
beforehand. Obviously I could ls() and get the name but as I have quite a few of these
I'd like to do it programmatically.
I thought something like this would work, but I get an error.
obj_name <- load("Robject.RData") # get the name of the loaded object
class(get(obj_name)) <- "myClass"
Error in class(get(obj_name)) <- " myClass " :
could not find function "get<-"
So I guess the question is how do I set the class of an R object when I only
have the object name as a character string?
(a) Actually, a wee experiment that I did indicates that your strategy actually
*works* despite the error message!!!
That is, you wind up with an object, named by obj_name, with class "myClass". I
don't understand this. Perhaps
someone more knowledgeable than I will enlighten us both.
It certainly won't work universally:
x <- 5
obj_name <- "x"
class(get(obj_name))<-"foo"
Error in class(get(obj_name)) <- "foo" : could not find function "get<-"
x
[1] 5
so further details of your wee experiments need to be revealed.
Hmmm. I did:
x <- 42
save(x,file="Robject.RData")
rm(list=ls())
obj_name <- load("Robject.RData")
class(get(obj_name)) <- "myClass"
x
and got:
[1] 42
attr(,"class")
[1] "myClass"
(also got the familiar error message).
When I did it your way --- without the saving and loading bit --- I got
the same result that you did. I.e. assigning the class that way did *not*
work (as one would expect it wouldn't!).
This is weird, n'est-ce pas?
Here is my
> sessionInfo()
R version 3.0.1 (2013-05-16)
Platform: x86_64-unknown-linux-gnu (64-bit)
locale:
[1] C
attached base packages:
[1] stats graphics grDevices utils datasets methods base
other attached packages:
[1] misc_0.0-15
cheers,
Rolf
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