[R] list of variables of an expression

[David Winsemius]

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)


>
> Regards,
> --
> Alberto
>
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David Winsemius, MD
West Hartford, CT