# isnan

Determine which array elements are NaN

## Syntax

``TF = isnan(A)``

## Description

example

````TF = isnan(A)` returns a logical array containing `1` (`true`) where the elements of `A` are `NaN`, and `0` (`false`) where they are not. If `A` contains complex numbers, `isnan(A)` contains `1` for elements with either real or imaginary part is `NaN`, and `0` for elements where both real and imaginary parts are not `NaN`.```

## Examples

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Create a row vector and determine which elements are `NaN`.

`A = 0./[-2 -1 0 1 2]`
```A = 1×5 0 0 NaN 0 0 ```
`TF = isnan(A)`
```TF = 1x5 logical array 0 0 1 0 0 ```

Create an array of complex numbers. Determine whether the complex numbers contain `NaN`.

`A = [2 + 1i, 1/0 + 3i, 1/2 - 1i*NaN]`
```A = 1×3 complex 2.0000 + 1.0000i Inf + 3.0000i 0.5000 + NaNi ```
`TF = isnan(A)`
```TF = 1x3 logical array 0 0 1 ```

Create an array and find the elements with `NaN` values.

`A = [1,3,5,7,NaN,10,NaN,4,6,8]`
```A = 1×10 1 3 5 7 NaN 10 NaN 4 6 8 ```
`TF = isnan(A)`
```TF = 1x10 logical array 0 0 0 0 1 0 1 0 0 0 ```

Index into `A` with `TF` to access the elements of `A` that are `NaN`. Replace the `NaN` values with 0.

`A(TF) = 0`
```A = 1×10 1 3 5 7 0 10 0 4 6 8 ```

## Input Arguments

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Input array, specified as a scalar, vector, matrix, or multidimensional array.

## Tips

• If `x` is a real scalar, exactly one of `isfinite(x)`, `isinf(x)`, and `isnan(x)` returns logical `1` (`true`).

• For a complex scalar `z`, `isinf(z)` and `isnan(z)` can both return logical 1. For example, `isinf(complex(Inf,NaN))` and `isnan(complex(Inf,NaN))` both return logical 1.

## Version History

Introduced before R2006a