How can I extract all the non-number symbols from an expression

Question

If I have an expression, let us say something like this:

Cos[3 x] + π/cofe Exp[y^(c  z)]

how can I get all non-number symbols in the expression which are:

{x, cofe, y, c, z}

I tried this:

Cases[Cos[3 x] + π/cofe Exp[y^(c  z)], _Symbol]

but it didn't work.

Possible duplicate: Is there an analogue of the Variables command for general expressions?. In short, does this do what you want?: Variables @ Level[expr, {-1}] (where expr is your expression). — Mr.Wizard, Jun 05 '14 at 08:02

score 11 · Accepted Answer · answered Jun 05 '14 at 04:35

11

expr = Cos[3 x] + \[Pi]/cofe Exp[y^(c z)];

Cases[expr, _Symbol?(! NumericQ[#] &), Infinity] // Union

(* {c, cofe, x, y, z} *)

In this case the Union is not necessary; however, in general it is needed to eliminate duplicates.

answered Jun 05 '14 at 04:35

Bob Hanlon

This is a nice answer and I am puzzled there is no built-in for this sort of thing but Variables (for polynomial expressions) is the closest there is. (+1) – gpap Jun 05 '14 at 07:33
@Bob Hanion, thanks. this is nice answer. – Basheer Algohi Jun 05 '14 at 15:53
An alternative: Cases[expr, Except[_?NumericQ, _Symbol], ∞] // Union – m_goldberg Jun 06 '14 at 00:53

1 Answers1