??
Or to add to what Peter Dalgaard said... (perhaps for the case of many more
functions)
Why eval(parse())? What's wrong with if then?
g <- function(fpost,x){if(fpost==1)f.1 else f.2 }(x)
or switch() if you have more than 2 possible arguments? I think your remarks
reinforce the wisdom of Thomas's "axiom" .
Bert Gunter
Genentech Nonclinical Statistics
South San Francisco, CA 94404
-----Original Message-----
From: r-help-bounces@(protected)
[mailto:r-help-bounces@(protected)
Sent: Friday, January 05, 2007 10:02 AM
To: r-help; rdiaz02@(protected)
Subject: [R] eval(parse(text vs. get when accessing a function
Dear All,
I've read Thomas Lumley's fortune "If the answer is parse() you should
usually
rethink the question.". But I am not sure it that also applies (and why) to
other situations (Lumley's comment
http://tolstoy.newcastle.edu.au/R/help/05/02/12204.html
was in reply to accessing a list).
Suppose I have similarly called functions, except for a postfix. E.g.
f.1 <- function(x) {x + 1}
f.2 <- function(x) {x + 2}
And sometimes I want to call f.1 and some other times f.2 inside another
function. I can either do:
g <- function(x, fpost) {
calledf <- eval(parse(text = paste("f.", fpost, sep = "")))
calledf(x)
## do more stuff
}
Or:
h <- function(x, fpost) {
calledf <- get(paste("f.", fpost, sep = ""))
calledf(x)
## do more stuff
}
Two questions:
1) Why is the second better?
2) By changing g or h I could use "do.call" instead; why would that be
better?
Because I can handle differences in argument lists?
Thanks,
R.
--
Ramón Díaz-Uriarte
Centro Nacional de Investigaciones Oncológicas (CNIO)
(Spanish National Cancer Center)
Melchor Fernández Almagro, 3
28029 Madrid (Spain)
Fax: +-34-91-224-6972
Phone: +-34-91-224-6900
http://ligarto.org/rdiaz
PGP KeyID: 0xE89B3462
(http://ligarto.org/rdiaz/0xE89B3462.asc)
**NOTA DE CONFIDENCIALIDAD** Este correo electrónico, y en s...{{dropped}}
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