question about deparse(substitute(...))

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-----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

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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