# Compare Categorical Array Elements

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

### Create Categorical Array

Create a categorical array.

```C = ["blue" "red" "green" "blue"; ... "blue" "green" "green" "blue"]; colors = categorical(C)```
```colors = 2x4 categorical blue red green blue blue green green blue ```

List the categories of the categorical array.

`categories(colors)`
```ans = 3x1 cell {'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 = 1x4 logical array 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 = 2x4 logical array 1 0 0 1 1 0 0 1 ```

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

### Convert to 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`. The elements in the categorical array remain the same.

`colors = categorical(colors,["red" "green" "blue"],Ordinal=true)`
```colors = 2x4 categorical blue red green blue blue green green blue ```

List the categories in `colors`.

`categories(colors)`
```ans = 3x1 cell {'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 = 2x1 logical array 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 = 2x4 logical array 0 1 1 0 0 1 1 0 ```

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