R help - Jul 2006 - deparse(substitute(foo))

I see that plot.default uses deparse(substitute(x)) to extract the
character name of an argument and put it on the vertical axis.

Hence:
foo <- 1:10
plot( foo )

will put the label "foo" on the vertical axis.

However, for a function that takes a "..." list as an input, I can
only
extract the first argument name:

x <- 1:10
y <- 10:20

foo <- function(...) {
  print(deparse(substitute(...)))
}

foo(x,y)

returns: 
> foo(x,y) 
[1] "x"
> 
and when I try to convert the list to a local variable and then extract
names, that doesn't work either:

x <- 1:10 
y <- 10:20 
 
foo <- function(...) { 
 
    x <- list(...) 
    print(deparse(substitute(names(x)))) 
} 
 
foo(x,y) 

returns:
> foo(x,y)
[1] "names(list(c(1, 2, 3, 4, 5, 6, 7, 8, 9, 10), c(10, 11, 12, 13, "
[2] "14, 15, 16, 17, 18, 19, 20)))"                                 
> 

Can someone suggest a way to extract the variable names when they are
passed as a list via "..." ?

Thanks,
Whit




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See ?match.call

On 7/27/06, Armstrong, Whit <whit.armstrong at hcmny.com>
wrote:
> I see that plot.default uses deparse(substitute(x)) to extract the
> character name of an argument and put it on the vertical axis.
>
> Hence:
> foo <- 1:10
> plot( foo )
>
> will put the label "foo" on the vertical axis.
>
> However, for a function that takes a "..." list as an input, I
can only
> extract the first argument name:
>
> x <- 1:10
> y <- 10:20
>
> foo <- function(...) {
>  print(deparse(substitute(...)))
> }
>
> foo(x,y)
>
> returns:
>
> > foo(x,y)
> [1] "x"
> >
>
> and when I try to convert the list to a local variable and then extract
> names, that doesn't work either:
>
> x <- 1:10
> y <- 10:20
>
> foo <- function(...) {
>
>    x <- list(...)
>    print(deparse(substitute(names(x))))
> }
>
> foo(x,y)
>
> returns:
>
> > foo(x,y)
> [1] "names(list(c(1, 2, 3, 4, 5, 6, 7, 8, 9, 10), c(10, 11, 12, 13,
"
> [2] "14, 15, 16, 17, 18, 19, 20)))"
> >
>
>
> Can someone suggest a way to extract the variable names when they are
> passed as a list via "..." ?
>
> Thanks,
> Whit
>
>
>
>
> This e-mail message is intended only for the named recipient(s) above. It
may contain confidential information. If you are not the intended recipient you
are hereby notified that any dissemination, distribution or copying of this
e-mail and any attachment(s) is strictly prohibited. If you have received this
e-mail in error, please immediately notify the sender by replying to this e-mail
and delete the message and any attachment(s) from your system. Thank you.
>
>
>
> ______________________________________________
> R-help at stat.math.ethz.ch mailing list
> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide
http://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.
>
>
>

On Thu, 2006-07-27 at 08:18 -0400, Armstrong, Whit
wrote:
> I see that plot.default uses deparse(substitute(x)) to extract the
> character name of an argument and put it on the vertical axis.
> 
> Hence:
> foo <- 1:10
> plot( foo )
> 
> will put the label "foo" on the vertical axis.
> 
> However, for a function that takes a "..." list as an input, I
can only
> extract the first argument name:
> 
> x <- 1:10
> y <- 10:20
> 
> foo <- function(...) {
>   print(deparse(substitute(...)))
> }
> 
> foo(x,y)
> 
> returns: 
> 
> > foo(x,y) 
> [1] "x"
> > 
> 
> and when I try to convert the list to a local variable and then extract
> names, that doesn't work either:
> 
> x <- 1:10 
> y <- 10:20 
>  
> foo <- function(...) { 
>  
>     x <- list(...) 
>     print(deparse(substitute(names(x)))) 
> } 
>  
> foo(x,y) 
> 
> returns:
> 
> > foo(x,y)
> [1] "names(list(c(1, 2, 3, 4, 5, 6, 7, 8, 9, 10), c(10, 11, 12, 13,
"
> [2] "14, 15, 16, 17, 18, 19, 20)))"
> > 
> 
> 
> Can someone suggest a way to extract the variable names when they are
> passed as a list via "..." ?
> 
> Thanks,
> Whit
Try this:

x <- 1:10 
y <- 10:20 
 
foo <- function(...) { 
   sapply(match.call()[-1], deparse)
} 

> foo(x, y)
[1] "x" "y"


HTH,

Marc Schwartz

That works perfectly.

Thanks,
Whit
 

-----Original Message-----
From: Marc Schwartz [mailto:MSchwartz at mn.rr.com] 
Sent: Thursday, July 27, 2006 8:41 AM
To: Armstrong, Whit
Cc: r-help at stat.math.ethz.ch
Subject: Re: [R] deparse(substitute(foo))

On Thu, 2006-07-27 at 08:18 -0400, Armstrong, Whit
wrote:
> I see that plot.default uses deparse(substitute(x)) to extract the 
> character name of an argument and put it on the vertical axis.
> 
> Hence:
> foo <- 1:10
> plot( foo )
> 
> will put the label "foo" on the vertical axis.
> 
> However, for a function that takes a "..." list as an input, I
can
> only extract the first argument name:
> 
> x <- 1:10
> y <- 10:20
> 
> foo <- function(...) {
>   print(deparse(substitute(...)))
> }
> 
> foo(x,y)
> 
> returns: 
> 
> > foo(x,y)
> [1] "x"
> > 
> 
> and when I try to convert the list to a local variable and then 
> extract names, that doesn't work either:
> 
> x <- 1:10
> y <- 10:20
>  
> foo <- function(...) {
>  
>     x <- list(...) 
>     print(deparse(substitute(names(x))))
> }
>  
> foo(x,y)
> 
> returns:
> 
> > foo(x,y)
> [1] "names(list(c(1, 2, 3, 4, 5, 6, 7, 8, 9, 10), c(10, 11, 12, 13,
"
> [2] "14, 15, 16, 17, 18, 19, 20)))"
> > 
> 
> 
> Can someone suggest a way to extract the variable names when they are 
> passed as a list via "..." ?
> 
> Thanks,
> Whit
Try this:

x <- 1:10
y <- 10:20 
 
foo <- function(...) { 
   sapply(match.call()[-1], deparse)
} 

> foo(x, y)
[1] "x" "y"


HTH,

Marc Schwartz





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and any attachment(s) is strictly prohibited. If you have received this e-mail
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