# isUnit

Determine if input is a symbolic unit

## Syntax

``tf = isUnit(expr)``

## Description

example

````tf = isUnit(expr)` returns logical `1` (`true`) if `expr` is a unit, or a product of powers of units, and logical `0` (`false`) if it is not.```

## Examples

### Determine if Input is a Unit

Determine if an expression is a symbolic unit by using `isUnit`.

Test if `3*u.m` is a symbolic unit, where ```u = symunit```. The `isUnit` function returns logical `0` (`false`) because `3*u.m` contains the symbolic number `3`.

```u = symunit; isUnit(3*u.m)```
```ans = logical 0```

Check if `u.m`, `u.mW`, and `x*u.Hz` are units, where `u = symunit`. The `isUnit` function returns the array `[1 1 0]`, meaning that the first two expressions are units but the third expression is not.

```syms x units = [u.m u.mW x*u.Hz]; isUnit(units)```
```ans = 1×3 logical array 1 1 0```

## Input Arguments

collapse all

Input, specified as a number, vector, matrix or multidimensional array, or a symbolic number, variable, vector, matrix, multidimensional array, function, or expression.

## Tips

• `1` represents a dimensionless unit. Hence, `isUnit(sym(1))` returns logical `1` (`true`).

## Version History

Introduced in R2017a