# Documentation

## Compare Categorical Array Elements

This example shows how to use relational operations with a categorical array.

### Create Categorical Array from Cell Array of Strings

Create a 2-by-4 cell array of strings.

```C = {'blue' 'red' 'green' 'blue';... 'blue' 'green' 'green' 'blue'}; colors = categorical(C) ```
```colors = blue red green blue blue green green blue ```

`colors` is a 2-by-4 categorical array.

List the categories of the categorical array.

```categories(colors) ```
```ans = 'blue' 'green' 'red' ```

### Determine If Elements Are Equal

Use the relational operator, `eq` (`==`), to compare the first and second rows of `colors`.

```colors(1,:) == colors(2,:) ```
```ans = 1 0 1 1 ```

Only the values in the second column differ between the rows.

### Compare Entire Array to String

Compare the entire categorical array, `colors`, to the string `'blue'` to find the location of all `blue` values.

```colors == 'blue' ```
```ans = 1 0 0 1 1 0 0 1 ```

There are four blue entries in `colors`, one in each corner of the array.

### Convert to an Ordinal Categorical Array

Add a mathematical ordering to the categories in `colors`. Specify the category order that represents the ordering of color spectrum, `red < green < blue`.

```colors = categorical(colors,{'red','green' 'blue'},'Ordinal',true) ```
```colors = blue red green blue blue green green blue ```

The elements in the categorical array remain the same.

List the discrete categories in `colors`.

```categories(colors) ```
```ans = 'red' 'green' 'blue' ```

### Compare Elements Based on Order

Determine if elements in the first column of `colors` are greater than the elements in the second column.

```colors(:,1) > colors(:,2) ```
```ans = 1 1 ```

Both values in the first column, `blue`, are greater than the corresponding values in the second column, `red` and `green`.

Find all the elements in `colors` that are less than `'blue'`.

```colors < 'blue' ```
```ans = 0 1 1 0 0 1 1 0 ```

The function `lt` (`<`) indicates the location of all `green` and `red` values with `1`.