[R] Evaluating expresssions as parameter values

[Erich Neuwirth]

Thanks, that completely solves the problem.

On Sep 22, 2009, at 10:27 PM, Gabor Grothendieck wrote:

> Try parse(text=...):
>
> f <- function(fo, data, groups) {
> 	g <- do.call("xyplot", list(as.formula(fo),
> 		groups = parse(text = groups), data))
> 	print(g)
> }
>
> f("yield ~ variety | site", data = barley, groups = "year")
>
>
>
> On Tue, Sep 22, 2009 at 4:20 PM, Erich Neuwirth
> <erich.neuwirth at univie.ac.at> wrote:
>> Thank you, this works for my example.
>> On Sep 22, 2009, at 9:17 PM, Gabor Grothendieck wrote:
>>
>> f <- function(fo, data, groups) {
>> g <- do.call("xyplot", list(as.formula(fo), groups = as.name 
>> (groups), data))
>> print(g)
>> }
>>
>> But xyplot allows expressions for the groups parameter also,
>> and using as.expression instead of as.name in your example does not  
>> work.
>> What is happening?
>>
>> f <- function(fo, data, groups) {
>> g <- do.call("xyplot", list(as.formula(fo), groups = as.expression 
>> (groups),
>> data))
>> print(g)
>> }
>>
>> f("yield ~ variety ~ site",barley,"year")
>> produces a very nicely labeled but empty plot.
>>
>