Is there a function that can extract a list of variables in an expression? For example, assume we have an expression


This expression has variables x, y and z. The result should be

{x, y, z}

. Is there a way to get this?

  • 9
    $\begingroup$ Variables command should work Variables[x^2 + y^3 + z] $\endgroup$ – user59583 Dec 18 '18 at 9:07

For polynomial expressions @Buddha_the_Scientist's suggestion Variables will work. For more general expressions

expr = x^2 + y^3 + z
DeleteDuplicates@Cases[expr, _Symbol, ∞]

Should do the trick in most situations.

  • $\begingroup$ Since all symbols are on level -1, you can use {-1} , instead of \[infinity]. $\endgroup$ – Fred Simons Dec 18 '18 at 11:14
  • $\begingroup$ Might want to include only symbols in the "Global`" context. I'd probably use Union instead of DeleteDuplicates to get them in canonical order. $\endgroup$ – Michael E2 Dec 18 '18 at 16:37

I like the following approach x):

expr = x^2 + y^3 + z;    
Select[DeleteDuplicates@Level[expr, Depth@expr], Head[#] == Symbol &]

the result is:

{x, y, z}

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