I am having trouble using the call()
function together with the namespace address operators ::
and :::
. Simply adding it to the function name as supplied for call()
produces an error when the call is evaluated, as this silly example shows:
> call("base::print", "Hi there")
`base::print`("Hi there")
> eval(call("base::print", "Hi there"))
Error in `base::print`("Hi there") :
could not find function "base::print"
For some reason, call()
adds backticks around the function name (probably because it contains non-standard characters), which seems to mess up everything. Here is what happens when the "address" is omitted:
> call("print", "Hi there")
print("Hi there")
> eval(call("print", "Hi there"))
[1] "Hi there"
I will very much appreciate any suggestions for how to solve this issue. Note however that I need to produce the code with call()
, as I am autogenerating code for rmarkdown code chunks, and I need to be able to specify the namespace, because I am using an unexported function from my package which I would really like to stay unexported.
Thanks for reading!
Update: I neglected to mention another property of the solution I am looking for (which I became aware of by reading Stéphane Laurent's otherwise great answer below): I am looking for a solution where the function definition is not copied into the call, which I believe rules out solutions using get()
. As an example of what I am trying to avoid, let's say we want to call qplot()
from ggplot2
. If we use eg getFromNamespace()
the call will look like this (with the middle part of the output omitted for making it easier to read):
> as.call(list(getFromNamespace("qplot", "ggplot2"), 1:10))
(function (x, y = NULL, ..., data, facets = NULL, margins = FALSE,
geom = "auto", xlim = c(NA, NA), ylim = c(NA, NA), log = "",
main = NULL, xlab = deparse(substitute(x)), ylab = deparse(substitute(y)),
asp = NA, stat = NULL, position = NULL)
{
if (!missing(stat))
warning("`stat` is deprecated", call. = FALSE)
if (!missing(position))
warning("`position` is deprecated", call. = FALSE)
if (!is.character(geom))
stop("`geom` must be a character vector", call. = FALSE)
argnames <- names(as.list(match.call(expand.dots = FALSE)[-1]))
arguments <- as.list(match.call()[-1])
env <- parent.frame()
#### A lot more code defining the function (omitted)#####
if (!missing(xlim))
p <- p + xlim(xlim)
if (!missing(ylim))
p <- p + ylim(ylim)
p
})(1:10)
The same thing happens if we instead use as.call(list(ggplot2::qplot, 1:10))
.
What I am looking for is something that produces the call ggplot2::qplot(1:10)
.
Maybe
> eval(as.call(list(getFromNamespace("print", "base"), "Hi there")))
[1] "Hi there"
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