Dynamically create a (convenience) function in a package
If you don't know the name of the attributes in advance, how can you know the function name to be able to call it? This seems like a very flawed approach. Also, I would discourage the use of eval(parse(text = )), it's almost always not the right way to do what you want to do. In your case, eval(bquote(function(x) attr(x, .(n)))) would be better. On Mon, Oct 30, 2023, 06:28 Sigbert Klinke <sigbert at wiwi.hu-berlin.de> wrote:
Hi,
n a package, I have a data object with attributes, and I want to
dynamically create a convenience function to access those attributes.
This way, instead of using attr(x, "number"), I would like to use
number(x).
Because I don't know in advance which attributes the data object may
have, I've used the following algorithm:
x <- structure(pi, number=exp(1))
a <- attributes(x)
for (n in names(a)) {
if (!exists(n, mode="function")) {
f <- eval(parse(text=sprintf("function(x) { attr(x, '%s') } ", n)))
assign(n, f, envir=.GlobalEnv)
}
}
number(x)
However, I believe modifying the global environment with this is not
allowed by CRAN for a package. Is there a way to implement such
functionality?
Thanks Sigbert
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