R help - Sep 2010 - 'programatically' list or call objects for use in a function?

Esteemed R users and developers,

How does one 'programatically' list or call objects for use in a
function?

For example, i thought i could do something better than this:

save(A.cwb, B.cwb, C.cwb, D.cwb, E.cwb, F.cwb, file="afile.RData")

with something like these-

prfxs <- c("A", "B", "C", "D",
"E", "F") #**
save(as.name(paste(prfxs, "cwb", sep=".")),
file="afile.RData")

or this-

do.call(save, paste(prfxs, "cwb", sep="."),
file="afile.RData")

Both failed.

#** And while i've got your attention- is there a 'letter
equivalent' to
seq() which would have worked nicely for prfxs? ie., letter.seq(A:F)

Thoughts and suggestions sincerely appreciated,

Karl



-- 
Karl Brand
Department of Genetics
Erasmus MC
Dr Molewaterplein 50
3015 GE Rotterdam
T +31 (0)10 704 3457 |F +31 (0)10 704 4743 |M +31 (0)642 777 268

On 11/09/2010 8:00 AM, Karl Brand wrote:
> Esteemed R users and developers,
> 
> How does one 'programatically' list or call objects for use in a
function?
It depends on the function.
> 
> For example, i thought i could do something better than this:
> 
> save(A.cwb, B.cwb, C.cwb, D.cwb, E.cwb, F.cwb,
file="afile.RData")
> 
> with something like these-
> 
> prfxs <- c("A", "B", "C", "D",
"E", "F") #**
> save(as.name(paste(prfxs, "cwb", sep=".")),
file="afile.RData")
For save, use list=paste(prfxs, "cwb", sep=".").
> 
> or this-
> 
> do.call(save, paste(prfxs, "cwb", sep="."),
file="afile.RData")
do.call wants a *list* of arguments, not a single vector of character 
strings.  You could construct a list of the names of the objects you 
want to save, but that's a pain.  Just use the list= argument (which 
doesn't want a list argument :-).
> 
> Both failed.
> 
> #** And while i've got your attention- is there a 'letter
equivalent' to
> seq() which would have worked nicely for prfxs? ie., letter.seq(A:F)
Not that I know of, but LETTERS[1:6] will give you the sequence, and 
it's easy to write a function that you'd call as
letter.seq("A", "F").
Having your function work as in your example would be messy.

Duncan Murdoch
> 
> Thoughts and suggestions sincerely appreciated,
> 
> Karl
> 
> 
>