[R] getting arg names in function calls?
spencer.graves at structuremonitoring.com
Wed Apr 9 01:52:48 CEST 2014
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 <-
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.
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(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-bounces at r-project.org [mailto:r-help-bounces at 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?
>> 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
>> 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.
>> R-help at r-project.org mailing list
>> PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
>> and provide commented, minimal, self-contained, reproducible code.
Spencer Graves, PE, PhD
President and Chief Technology Officer
Structure Inspection and Monitoring, Inc.
751 Emerson Ct.
San José, CA 95126
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