[R] Accesing the name of an assigned object in a function

[Gabor Grothendieck]

Arne Henningsen <ahenningsen <at> email.uni-kiel.de> writes:

> 
> Hi Hendrik,
> 
> if I understand you right, match.call() can help you.
> 
> All the best,
> Arne
> 
> On Wednesday 01 September 2004 12:13, Henrik Andersson wrote:
> > I want to use the name that I assign to an object in the function that
> > produces the output, somewhat like below:
> >
> > stupid.function <- function(input){
> >  [body]
> >  cat("Summarized output is ", output$summary, "Full output is    given
> > by typing", assigned.name, "\n")
> >  }
> >
> > assigned.name <- stupid.function(whatever)
> >
> >
> > or another example is a function that sinks the results to a text file
> > and names it assigned.name.txt .
> >
> > I checked the help for function, <-, assign but could not find it, is it
> >   possible ?



As far as I know you are going to have to pass the assigned.name to the
function although there are a number of tricks that can make this a bit
nicer.  For example, run this:

example(lm)

# which has the effect of defining lm.D9 which we will use for our
# examples below.  Using that:

#### 1
set1 <- function(x, value) {
	name <- as.character(substitute(x))
	print(summary(value)$fstatistic)
	cat("That was F and df.  For more info type", name, "\n")
	assign(name, value, parent.frame())
	invisible(value)
}
set1(x, lm.D9)
x
	
# We can make this a bit prettier this way:

#### 2
set2 <- structure(NA,class="set2")
"[<-.set2" <- function(tmp,x,value) {
	name <- as.character(substitute(x))
	print(summary(value)$fstatistic)
	cat("That was F and df.  For more info type", name, "\n")
	assign(name, value, parent.frame())
	tmp
}

# now we can write:
set2[xx] <- lm.D9
xx

# Another strategy might be to use a global variable to store the
# last output from your function:

#### 3
set3 <- function(value) {
	name <- as.character(substitute(x))
	print(summary(value)$fstatistic)
	cat("That was F and df.  For more info type .set3\n")
	assign(".set3", value, .GlobalEnv)
	invisible(value)
}
xxx <- set3(lm.D9)  # or just set3(lm.D9)
.set3