# Relational Operator

Perform specified relational operation on inputs

Libraries:
Simulink / Commonly Used Blocks
Simulink / Logic and Bit Operations
HDL Coder / Commonly Used Blocks
HDL Coder / HDL Floating Point Operations
HDL Coder / Logic and Bit Operations

## Description

The Relational Operator block performs the specified relational operation on the input. The value you choose for the Relational operator parameter determines whether the block accepts one or two input signals.

### Two-Input Mode

By default, the Relational Operator block compares two inputs using the Relational operator parameter that you specify. The first input corresponds to the top input port and the second input to the bottom input port. (See Identify Port Location on Rotated or Flipped Block for a description of the port order for various block orientations.)

You can specify one of the following operations in two-input mode:

OperationDescription

`==`

True if the first input is equal to the second input

`~=`

True if the first input is not equal to the second input

`<`

True if the first input is less than the second input

`<=`

True if the first input is less than or equal to the second input

`>=`

True if the first input is greater than or equal to the second input

`>`

True if the first input is greater than the second input

You can specify inputs as scalars, arrays, or a combination of a scalar and an array.

For...The output is...
Scalar inputsA scalar
Array inputsAn array of the same dimensions, where each element is the result of an element-by-element comparison of the input arrays
Mixed scalar and array inputsAn array, where each element is the result of a comparison between the scalar and the corresponding array element

If the relational operation can be efficiently and accurately represented on the hardware board, this efficient representation is used. Otherwise, both operands are cast to a common type using overflow saturation and the specified rounding mode.

You can specify the output data type using the Output data type parameter. The output equals `1` for true and `0` for false.

Tip

Select an output data type that represents zero exactly. Data types that satisfy this condition include signed and unsigned integers and any floating-point data type.

### One-Input Mode

When you select one of the following operations for Relational operator, the block switches to one-input mode.

OperationDescription

`isInf`

True if the input is `Inf`

`isNaN`

True if the input is `NaN`

`isFinite`

True if the input is finite

For an input that is not floating point, the block produces the following output.

Data TypeOperationBlock Output
• Fixed point

• Boolean

• Built-in integer

`isInf`

False

`isNaN`

False

`isFinite`

True

### Rules for Data Type Propagation

The following rules apply for data type propagation when your block has one or more input ports with unspecified data types.

When the block is in...And...The block uses...
Two-input modeBoth input ports have unspecified data types `double` as the default data type for both inputs
One input port has an unspecified data typeThe data type from the specified input port as the default data type of the other port
One-input modeThe input port has an unspecified data type `double` as the default data type for the input

## Ports

### Input

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First input signal, specified as a scalar, vector, or matrix.

Data Types: `half` | `single` | `double` | `int8` | `int16` | `int32` | `int64` | `uint8` | `uint16` | `uint32` | `uint64` | `Boolean` | `fixed point` | `enumerated`

Second input signal, specified as a scalar, vector, or matrix.

#### Dependencies

To enable this port, set the Relational operator to `==`, `~=`, `<`, `<=`, `>=`, or `>`.

Data Types: `half` | `single` | `double` | `int8` | `int16` | `int32` | `int64` | `uint8` | `uint16` | `uint32` | `uint64` | `Boolean` | `fixed point` | `enumerated`

### Output

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Output signal, consisting of zeros and ones, with the same dimensions as the input. You control the output data type with the Output data type parameter.

Data Types: `half` | `single` | `double` | `int8` | `int16` | `int32` | `int64` | `uint8` | `uint16` | `uint32` | `uint64` | `Boolean` | `fixed point` | `enumerated`

## Parameters

expand all

### Main

Specify the operation for comparing two inputs or determining the signal type of one input.

• `==` — True if the first input is equal to the second input

• `~=` — True if the first input is not equal to the second input

• `<` — True if the first input is less than the second input

• `<=` — True if the first input is less than or equal to the second input

• `>=` — True if the first input is greater than or equal to the second input

• `>` — True if the first input is greater than the second input

• `isInf` — True if the input is `Inf`

• `isNaN` — True if the input is `NaN`

• `isFinite` — True if the input is finite

`==` and `~=` support complex numbers for simulation and code generation.

#### Programmatic Use

 Block Parameter: `Operator` Type: character vector Values: ```'==' | '~=' | '<' | '<=' | '>=' | '>' | 'isInf' | 'isNaN' | 'isFinite'``` Default: `'<='`

Select to enable zero-crossing detection. For more information, see Zero-Crossing Detection.

#### Programmatic Use

 Parameter: `ZeroCross` Type: character vector, string Values: `'on'` | `'off'` Default: `'on'`

Specify the time interval between samples. To inherit the sample time, set this parameter to `-1`. For more information, see Specify Sample Time.

#### Dependencies

This parameter is visible only if you set it to a value other than `-1`. To learn more, see Blocks for Which Sample Time Is Not Recommended.

#### Programmatic Use

 Block Parameter: `SampleTime` Type: string scalar or character vector Default: `"-1"`

### Data Type

To require that all block inputs have the same data type, select this check box. When you clear this check box, the inputs can have different data types.

#### Dependencies

This check box is not available when you set Relational operator to `isInf`, `isNaN`, or `isFinite` because, in those modes, the block only has one input port.

#### Programmatic Use

 Block Parameter: `InputSameDT` Type: character vector Values: `'off' | 'on` Default: `'off'`

Specify the output data type. When you select:

• `boolean` — The block output has data type `boolean`.

• ```Inherit: Logical (see Configuration Parameters: Optimization)``` — The block uses the Implement logic signals as Boolean data configuration parameter to specify the output data type (see Implement logic signals as Boolean data (vs. double)) .

Note

This option supports models created before the `boolean` option was available. Use one of the other options, preferably `boolean`, for new models.

• `fixdt(1,16)` — The block output has the specified fixed-point data type `fixdt(1,16)`.

Tip

The Data Type Assistant helps you set data attributes. To use the Data Type Assistant, click . For more information, see Specify Data Types Using Data Type Assistant.

• `<data type expression>` — The block output has the data type you specify as a data type expression, for example, `Simulink.NumericType`.

Tip

To enter a built-in data type (`double`, `single`, `int8`, `uint8`, `int16`, `uint16`, `int32`, or `uint32`), enclose the expression in single quotes. For example, enter `'double'` instead of `double`.

#### Programmatic Use

 Block Parameter: `OutDataTypeStr` Type: character vector Values: ```'Inherit: Logical (see Configuration Parameters: Optimization)' | 'boolean' | 'fixdt(1,16)' | ''``` Default: `'boolean'`

Specify the rounding mode for fixed-point operations. You can select:

`Ceiling`

Rounds positive and negative numbers toward positive infinity. Equivalent to the MATLAB® `ceil` function.

`Convergent`

Rounds number to the nearest representable value. If a tie occurs, rounds to the nearest even integer. Equivalent to the Fixed-Point Designer™ `convergent` function.

`Floor`

Rounds positive and negative numbers toward negative infinity. Equivalent to the MATLAB `floor` function.

`Nearest`

Rounds number to the nearest representable value. If a tie occurs, rounds toward positive infinity. Equivalent to the Fixed-Point Designer `nearest` function.

`Round`

Rounds number to the nearest representable value. If a tie occurs, rounds positive numbers toward positive infinity and rounds negative numbers toward negative infinity. Equivalent to the Fixed-Point Designer `round` function.

`Simplest`

Chooses between rounding toward floor and rounding toward zero to generate rounding code that is as efficient as possible.

`Zero`

Rounds number toward zero. Equivalent to the MATLAB `fix` function.

For more information, see Rounding (Fixed-Point Designer).

#### Programmatic Use

 Block Parameter: `RndMeth` Type: character vector Values: ```'Ceiling' | 'Convergent' | 'Floor' | 'Nearest' | 'Round' | 'Simplest' | 'Zero'``` Default: `'Simplest'`

Select the category of data to specify.

• `Built in` — Specifies built-in data types. Selecting `Built in` enables `boolean`.

• `Inherit` — Specifies inheritance rules for data types. Selecting `Inherit` enables ```Logical (see Configuration Parameters: Optimization)```.

• `Fixed point` — Specifies fixed-point data types.

• `Expression` — Specifies expressions that evaluate to data types.

#### Dependencies

To enable this parameter, click the button.

Select the data type override mode for this signal.

• When you select `Inherit`, Simulink inherits the data type override setting from its context, that is, from the block, `Simulink.Signal` object or Stateflow® chart in Simulink® that is using the signal.

• When you select `Off`, Simulink ignores the data type override setting of its context and uses the fixed-point data type specified for the signal.

For more information, see Specify Data Types Using Data Type Assistant in the Simulink documentation.

#### Dependencies

To enable this parameter, set Mode to ```Built in``` or `Fixed point`.

#### Tips

The ability to turn off data type override for an individual data type provides greater control over the data types in your model when you apply data type override. For example, you can use this option to ensure that data types meet the requirements of downstream blocks regardless of the data type override setting.

Specify whether you want the fixed-point data as signed or unsigned. Signed data can represent positive and negative values, but unsigned data represents positive values only. For more information, see Specifying a Fixed-Point Data Type.

#### Dependencies

To enable this parameter, set Mode to `Fixed point`.

Specify the bit size of the word that holds the quantized integer. For more information, see Specifying a Fixed-Point Data Type.

#### Dependencies

To enable this parameter, set Mode to `Fixed point`.

Specify the method for scaling your fixed-point data to avoid overflow conditions and minimize quantization errors. Specifying `Integer` has the same result as specifying a binary point location and setting the fraction length to `0`.

#### Dependencies

To enable this parameter, click the button and set Mode to `Fixed point`.

## Block Characteristics

 Data Types `Boolean` | `double` | `enumerated` | `fixed point` | `half` | `integer` | `single` Direct Feedthrough `yes` Multidimensional Signals `yes` Variable-Size Signals `yes` Zero-Crossing Detection `yes`

## Version History

Introduced before R2006a