R expression variable list

Question

Is it possible to get a vector or list of variables in an expression?

For instance:

e <- expression(2 * x^2 + y)

The desired output:

('x', 'y')

Is it possible? Or is it necessary to input variable names manually?

You'd be slightly better off creating the simpler call object here: e <- quote(2 * x^2 + y) — hadley
– hadley, Commented Dec 3, 2013 at 16:19

James · Accepted Answer · 2013-12-03 15:28:37Z

9

Use all.vars:

all.vars(e)
[1] "x" "y"

answered Dec 3, 2013 at 15:28

James

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1 Comment

And in case you want to write variations, adv-r.had.co.nz/… describes how to do it with recursive R code.