[R] call lattice function in a function passing

Ryan Hafen
Thu, 11 Dec 2008 15:13:57 -0000

>
> If however I wanted to call the function "densityplot" within a
function and
> pass the "groups" argument as an argument of that function, how
would I have
> to proceed? It is not as straightforward as
>
> f <- function(data, groupvar) {
>   densityplot(~ x, data, groups = groupvar)
> }
>
> probably because the lattice function "densityplot.formula"
preprocesses
> the "groups" argument with
>
> groups <- eval(substitute(groups), data, environment(formula))
>
> It there a way how I could pass the "groups" argument in the
function "f"?

Here's one approach.  Pass the 'groups' variable as a character,
then find
that variable in the data frame and rename it.

d <- data.frame(x = rnorm(100), y = c("a", "b"))

f <- function(data, groupvar) {
	names(data)[which(names(data) == groupvar)] <- "gp"
  	densityplot(~ x, data, groups = gp)
}

f(d, groupvar="y")