[R] save object interactively

[solares@unsl.edu.ar]

Hello, it wanted to know as I can keep to save a object of R in interactive 
form, in which I can put the name of the file in a window of I talk, and 
not to have to create it, a badly serious example:

 x<-c(1,2,3,4)
> nbre<-"x.Rdata"
> f<-file.choose()
Error in file.choose() : file choice cancelled
> f
Error: Object "f" not found
> file.create(nbre)
[1] TRUE
> f<-file.choose()
> save(nbre,file=f)

But I should create the file before electing it, there is not form of 
opening a window of I talk and to keep with a name that I can put in that 
window?  Does not something exist as 
file.choose.save?  . Thanks Ruben