On Jun 15, 2010, at 5:07 PM, David Winsemius wrote:
>
> On Jun 15, 2010, at 5:45 PM, Alberto Lusiani wrote:
>
>> I would like to get the list of variables of an expression: is that
>> possible? I searched the help and the web without success. In
>> practice, given an expression like
>>
>> expr = parse(text="x^2+y^3")
>>
>> I would like to have a function such as:
>>
>> vars(expr)
>>
>> returns
>>
>> c("x", "y") or a list like the one returned by formals().
>
> attr(terms(formula(paste("~", "x^2+y^3"))), "variables")
> # returns list(x, y)
>
A little easier:
> all.vars(expression(x^2+y^3))
[1] "x" "y"
See ?all.vars for more information.
HTH,
Marc Schwartz
______________________________________________
R-help@r-project.org mailing list
https://stat.ethz.ch/mailman/listinfo/r-help
PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
and provide commented, minimal, self-contained, reproducible code.
