## Find Symbolic Variables in Expressions, Functions, Matrices

To find symbolic variables in an expression, function, or matrix, use `symvar`. For example, find all symbolic variables in symbolic expressions `f` and `g`:

```syms a b n t x f = x^n; g = sin(a*t + b); symvar(f)```
```ans = [ n, x]```

Here, `symvar` sorts all returned variables alphabetically. Similarly, you can find the symbolic variables in `g` by entering:

`symvar(g)`
```ans = [ a, b, t]```

`symvar` also can return the first `n` symbolic variables found in a symbolic expression, matrix, or function. To specify the number of symbolic variables that you want `symvar` to return, use the second parameter of `symvar`. For example, return the first two variables found in symbolic expression `g`:

`symvar(g, 2)`
```ans = [ b, t]```

Notice that the first two variables in this case are not `a` and `b`. When you call `symvar` with two arguments, it finds symbolic variables by their proximity to `x` before sorting them alphabetically.

When you call `symvar` on a symbolic function, `symvar` returns the function inputs before other variables.

```syms x y w z f(w, z) = x*w + y*z; symvar(f)```
```ans = [ w, z, x, y]```

When called with two arguments for symbolic functions, `symvar` also follows this behavior.

`symvar(f, 2)`
```ans = [ w, z]```

### Find a Default Symbolic Variable

If you do not specify an independent variable when performing substitution, differentiation, or integration, MATLAB® uses a default variable. The default variable is typically the one closest alphabetically to `x` or, for symbolic functions, the first input argument of a function. To find which variable is chosen as a default variable, use the `symvar(f, 1)` command. For example:

```syms s t f = s + t; symvar(f, 1)```
```ans = t```
```syms sx tx f = sx + tx; symvar(f, 1)```
```ans = tx```

For more information on choosing the default symbolic variable, see `symvar`.

#### Mathematical Modeling with Symbolic Math Toolbox

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