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# isfield

Determine whether input is structure array field

## Syntax

```tf = isfield(S,fieldname) tf = isfield(S,C) ```

## Description

`tf = isfield(S,fieldname)` examines structure `S` to see if it includes the field specified by `fieldname`. Output `tf` is set to logical `1` (`true`) if `S` contains the field, or logical `0` (`false`) if not. If `S` is not a structure array, `isfield` returns `false`. The input argument `fieldname` can be a character vector or a string scalar.

`tf = isfield(S,C)` examines structure `S` for multiple fieldnames as specified in `C`, and returns an array of logical values to indicate which of these fields are part of the structure. Elements of output array `tf` are set to a logical 1 (`true`) if the corresponding element of `C` holds a fieldname that belongs to structure `S`. Otherwise, logical 0 (`false`) is returned in that element. In other words, if structure `S` contains the field specified in `C(m,n)`, `isfield` returns a logical 1 (`true`) in `tf(m,n)`. The input argument `C` can be a cell array of character vectors or a string array.

### Note

`isfield` returns `false` if the `field` or `fieldnames` input is empty.

## Examples

### Example 1 — Single Fieldname Syntax

Given the following MATLAB® structure,

```patient.name = 'John Doe'; patient.billing = 127.00; patient.test = [79 75 73; 180 178 177.5; 220 210 205];```

`isfield` identifies `billing` as a field of that structure.

```isfield(patient,'billing') ans = 1```

### Example 2 — Multiple Fieldname Syntax

Check structure `S` for any of four possible fieldnames. Only the first is found, so the first element of the return value is set to `true`:

```S = struct('one', 1, 'two', 2); fields = isfield(S, {'two', 'pi', 'One', 3.14}) fields = 1 0 0 0```