Hi, Bill:
Thanks for the reply. Unfortunately, I don't see how that solves
the example I gave of extracting "plot(x=0, y=1)" from tstFn <-
function()plot(0, 1).
As I noted, body(tstFn) returns "plot(0, 1)" as an "language"
object of class "call". My challenge is to convert that into something
similar, with explicit names for the arguments.
Any thoughts?
Spencer
On 4/7/2014 3:18 PM, William Dunlap wrote:
Look at match.call(). E.g.,
> f <- function(x, y = log2(x), ...) match.call()
> f()
f()
> f(1, x=2, anotherArg=3, 4)
f(x = 2, y = 1, anotherArg = 3, 4)
or, using its 'definition' and 'call' arguments directly
> match.call(function(x, y, ...)NULL, quote(foo(1, x=2, extraArg=3, 4)))
foo(x = 2, y = 1, extraArg = 3, 4)
> match.call(function(x, y, ...)NULL, quote(foo(1, x=2, extraArg=3, 4)),
expand.dots=FALSE)
foo(x = 2, y = 1, ... = list(extraArg = 3, 4))
Bill Dunlap
TIBCO Software
wdunlap tibco.com
-----Original Message-----
From: r-help-boun...@r-project.org [mailto:r-help-boun...@r-project.org] On
Behalf
Of Spencer Graves
Sent: Monday, April 07, 2014 3:05 PM
To: R list
Subject: [R] getting arg names in function calls?
How can I convert "plot(0, 1)" into "plot(x=0, y=1)"?
More generally, how can I get argument names assigned to function
calls in "language" objects?
Example:
tstFn <- function()plot(0, 1)
bo <- body(tstFn)
tstFnxy <- function()plot(x=0, y=1)
boxy <- body(tstFnxy)
Is there a function that will modify "bo" to match "boxy"?
My current solution requires me to know the names of the
arguments for "plot" (in this example). I'd prefer a more general
solution.
Thanks,
Spencer
p.s. I'm trying to create an animation by repeatedly calling a function
that contains something like text(0, 1, "abc"). By computing on the
language object 'text(0, 1, "abc")', I can call text(0, 1, 'a') the
first time, text(0, 1, 'ab') the second, and text(0, 1, 'abc') the
third. The function will be more general if I can get the names of the
arguments as just described.
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--
Spencer Graves, PE, PhD
President and Chief Technology Officer
Structure Inspection and Monitoring, Inc.
751 Emerson Ct.
San José, CA 95126
ph: 408-655-4567
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______________________________________________
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PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
and provide commented, minimal, self-contained, reproducible code.
