[R] Pass character vector to function argument

[Kevin Ummel]

Sorry, I shouldn't have used 'sum' as an example; I am looking for a solution in the case of functions that do not result in simple vectors or matrices.

The "real-world" example is something like the following using the 'raster' package, though (I think) any command producing an S4 object could be a candidate:

r1 <- raster(system.file("external/test.grd", package="raster"))*1
r2 <- raster(system.file("external/test.grd", package="raster"))*2

obs=objects(pattern=glob2rx("r?"))

#Would like to generate the equivalent of...

stack(r1,r2)

...using a variation of obs as an argument to 'stack' (potentially very long).

Cheers,
Kevin 


On Nov 16, 2010, at 5:07 PM, David Winsemius wrote:

> 
> On Nov 16, 2010, at 10:34 AM, Kevin Ummel wrote:
> 
>> A bit embarrassed to post this seemingly trivial question, but I can't find anything in the archive that's quite relevant:
>> 
>> a1=1
>> a2=2
>> 
>> obs=objects(pattern=glob2rx("a?"))
>> 
>> I want to utilize 'obs' as a function argument to produce something like:
>> 
>> sum(a1,a2)
>> 
> 
> ?get
> > sum(sapply(obs, get))
> [1] 3
> 
> 
>> Obviously, sum(obs) doesn't work, but I've tried variations of 'eval', 'parse', 'mget', and 'noquote' without success. What am I missing?
>> 
>> Thanks,
>> Kevin
>> 
> -- 
> David Winsemius, MD
> West Hartford, CT
>