[R] Deparsing part of a list argument

[Steven McKinney]

This is one way to implement the idea 
the other responses point at:


> myfun <- function(funlist, vec){
+     tmp <- lapply(funlist, function(x)do.call(x, args = list(vec)))
+     names(tmp)[names(tmp) == ""] <-
+       sapply(match.call()[[2]], deparse)[-1][names(tmp) == ""]
+     tmp
+ }
> 

> 
> myfun(list("Summation" = sum, prod, "Absolute value" = abs), c(1, 4, 6,
+ 7))
$Summation
[1] 18

$prod
[1] 168

$`Absolute value`
[1] 1 4 6 7





Steven McKinney

Statistician
Molecular Oncology and Breast Cancer Program
British Columbia Cancer Research Centre

email: smckinney +at+ bccrc +dot+ ca

tel: 604-675-8000 x7561

BCCRC
Molecular Oncology
675 West 10th Ave, Floor 4
Vancouver B.C. 
V5Z 1L3
Canada




-----Original Message-----
From: r-help-bounces at r-project.org on behalf of Andrew Smith
Sent: Thu 10/25/2007 2:38 PM
To: r-help at stat.math.ethz.ch
Subject: [R] Deparsing part of a list argument
 
Here's a simple example of the type of function I'm trying to write,
where the first argument is a list of functions:

myfun <- function(funlist, vec){
     tmp <- lapply(funlist, function(x)do.call(x, args = list(vec)))
     names(tmp) <- names(funlist)
     tmp
}

> myfun(list("Summation" = sum, prod, "Absolute value" = abs), c(1, 4, 6, 7))
$Summation
[1] 18

[[2]]
[1] 168

$`Absolute value`
[1] 1 4 6 7


What I would like is for the names of the result to be the same as the
names of funlist (as is the case in components 1 and 3 above), but if
some components of funlist are unnamed, I would like the default name
in the result to be the name of the actual function used.  So in the
above example, I want the name of the second component to default to
'prod', since funlist[[2]] has no name.

 But the problem is that I can't get the function names corresponding
to the unnamed elements of funlist by using the usual
deparse(substitute)) trick, since they're part of a list which is
treated as one big argument.  So deparse(substitute(funlist)) just
gives me one big character string of all the functions, and I'm not
sure how I can use that to get just the functions that aren't named.
Any ideas?

Thanks,
Andrew

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