R help - Jan 2011 - question about deparse(substitute(...))

Dear R helpers:

I like to apply deparse(substitute()) on multiple arguments to collect the
names of the arguments into a character vector.
I used function test.fun as below. it works when there is only one input
argument. but it does not work for multiple arguements. can someone kindly
help?

test.fun <- function(...){deparse(substitute(...))}
test.fun(x) #this works
test.fun(x,y,z) # I like c('x','y','z') be the output,
but cannot get it.

Thanks in advance.

-Sean

	[[alternative HTML version deleted]]

> -----Original Message-----
> From: r-help-bounces at r-project.org 
> [mailto:r-help-bounces at r-project.org] On Behalf Of Sean Zhang
> Sent: Thursday, January 13, 2011 4:37 PM
> To: r-help at r-project.org
> Subject: [R] question about deparse(substitute(...))
> 
> Dear R helpers:
> 
> I like to apply deparse(substitute()) on multiple arguments 
> to collect the
> names of the arguments into a character vector.
> I used function test.fun as below. it works when there is 
> only one input
> argument. but it does not work for multiple arguements. can 
> someone kindly
> help?
> 
> test.fun <- function(...){deparse(substitute(...))}
> test.fun(x) #this works
> test.fun(x,y,z) # I like c('x','y','z') be the
output, but
> cannot get it.
One way is:
   > f <- function(...) lapply(substitute(placeholderFunction(...))[-1],
deparse)
   > f(x, log(y), (function(a){a+a^2/2+a^3/6})(z))
   [[1]]
   [1] "x"

   [[2]]
   [1] "log(y)"

   [[3]]
   [1] "(function(a) {"       
   [2] "    a + a^2/2 + a^3/6"
   [3] "})(z)"                

Use paste(collapse="\n",s) or s[1] on
deparse's output if you require one
string per input.

Bill Dunlap
Spotfire, TIBCO Software
wdunlap tibco.com  
> 
> Thanks in advance.
> 
> -Sean
> 
> 	[[alternative HTML version deleted]]
> 
> ______________________________________________
> R-help at r-project.org 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, Jan 13, 2011 at 7:36 PM, Sean Zhang <seanecon at gmail.com>
wrote:
> Dear R helpers:
>
> I like to apply deparse(substitute()) on multiple arguments to collect the
> names of the arguments into a character vector.
> I used function test.fun as below. it works when there is only one input
> argument. but it does not work for multiple arguements. can someone kindly
> help?
>
> test.fun <- function(...){deparse(substitute(...))}
> test.fun(x) #this works
> test.fun(x,y,z) # I like c('x','y','z') be the
output, but cannot get it.
>
Try this:
> test.fun.2 <- function(...) sapply(match.call()[-1], deparse)
> test.fun.2(x, y, z)
[1] "x" "y" "z"

You could consider replacing sapply with lapply since it will return a
list of vectors if the arguments are complex -- so that would
consistently return a list.

-- 
Statistics & Software Consulting
GKX Group, GKX Associates Inc.
tel: 1-877-GKX-GROUP
email: ggrothendieck at gmail.com