Find Nonzero Elements

Find nonzero elements in array

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Libraries:
Simulink / Math Operations

Description

The Find Nonzero Elements block locates all nonzero elements of the input signal and returns the linear indices of those elements. If the input is a multidimensional signal, the Find Nonzero Elements block can also return the subscripts of the nonzero input elements. In both cases, you can show an output port with the nonzero input values.

The Find Nonzero Elements block outputs a variable-size signal. The sample time for any variable-size signal must be discrete. If your model does not already use a fixed-step solver, you may need to select a fixed-step solver in the Configuration Parameters dialog. For more information, see Compare Solvers and Choose a Solver.

Examples

Find Nonzero Elements in an Array

This example shows how to use the Find block to find nonzero elements in an array. In the following model, the block is configured to output both the one-based linear index and the value of each nonzero element.

Extended Examples

Parallel Channel Power Allocation

A potential use of the Find Nonzero Elements block. This block outputs a variable-size signal containing the indices of the nonzero values of the input.

• Open Model

Ports

Input

Port_1 — Input signal

scalar | vector | matrix | N-D array

Input signal from which the block finds all nonzero elements.

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

Output

Port_1 — Indices of nonzero elements

variable-size signal

The Find Nonzero Elements block outputs the indices of nonzero elements as a variable-size signal. You control the data type of the output using the Output data type block parameter.

Dependencies

By default, the block outputs linear indices from the first output port. When you change the Index output format to Subscripts, the block instead provides the element indices of a two-dimension or larger signal in a subscript form. In this mode, you must specify the Number of input dimensions, and the block creates a separate output port for each dimension.

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

Port_2 — Values of nonzero elements

variable-size signal

The Find block can optionally output the values of all nonzero elements as a variable-size signal.

Dependencies

To enable this port, select Show output port for nonzero input values.

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

Parameters

Main

Index output format — Format for indices of nonzero elements

Linear indices (default) | Subscripts

Select the output format for the indices of the nonzero input values.

• Selecting Linear indices provides the element indices of any dimension signal in a vector form. For one dimension (vector) signals, indices correspond to the position of nonzero values within the vector. For signals with more than one dimension, the conversion of subscripts to indices is along the first dimension. You do not need to know the signal dimension of the input signal.

• Selecting Subscripts provides the element indices of a two-dimension or larger signal in a subscript form. Because the block shows an output port for each dimension, this option requires you to specify the Number of input dimensions.

Programmatic Use

Block Parameter: IndexOutputFormat

Type: character vector

Values: 'Linear indices' | 'Subscripts'

Default: 'Linear indices'

Number of input dimensions — Number of dimensions for the input signal

1 (default) | scalar

Specify the number of dimensions for the input signal as a positive integer value from 1 to 32.

Dependencies

To enable this parameter, set Index output format to Subscripts.

Programmatic Use

Block Parameter: NumberOfInputDimensions

Type: character vector

Values: scalar

Default: '1'

Index mode — Specify zero- or one-based indexing

Zero-based (default) | One-based

Specify the indexing mode as Zero-based or One-based.

• For Zero-based indexing, an index of 0 specifies the first element of the input vector. An index of 1 specifies the second element, and so on.

• For One-based indexing, an index of 1 specifies the first element of the input vector. An index of 2, specifies the second element, and so on.

Programmatic Use

Block Parameter: IndexMode

Type: character vector

Values: 'Zero-based' | 'One-based'

Default: 'Zero-based'

Show output port for nonzero input values — Enable output port for nonzero values

off (default) | on

Show or hide the output port for nonzero input values.

• When you clear this check box (off), the block hides the output port for nonzero input values.

• When you select this check box (on), the block displays the output port for nonzero input values. The additional output port provides values of the nonzero input elements.

Programmatic Use

Block Parameter: ShowOutputPortForNonzeroInputValues

Type: character vector

Values: 'on' | 'off'

Default: 'off'

Sample time (-1 for inherited) — Interval between samples

-1 (default) | scalar | vector

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

To set the block parameter value programmatically, use the set_param function.

Parameter:	SampleTime
Values:	"-1" (default) | scalar or vector in quotes

Data Types

Output data type — Output data type

Inherit: Inherit via internal rule (default) | int8 | uint8 | int16 | uint16 | int32 | uint32 | int64 | uint64 | fixdt(1,16) | <data type expression>

Specify the output data type.

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.

Programmatic Use

Block Parameter: OutDataTypeStr

Type: character vector

Values: 'Inherit: Inherit via internal rule' | 'int8' | 'uint8' | 'int16' | 'uint16' | 'int32' | 'uint32' | 'int64' | 'uint64' | 'fixdt(1,16)' | '<data type expression>'

Default: 'Inherit: Inherit via internal rule'

Mode — Select data type mode

Inherit (default) | Built in | Fixed Point

Select the category of data to specify.

• Inherit — Inheritance rules for data types. Selecting Inherit enables a second menu/text box to the right where you can select the inheritance mode.

• Built in — Built-in data types. Selecting Built in enables a second menu/text box to the right where you can select a built-in data type.

• Fixed point — Fixed-point data types. Selecting Fixed point enables additional parameters that you can use to specify a fixed-point data type.

• Expression — Expressions that evaluate to data types. Selecting Expression enables a second menu/text box to the right, where you can enter the expression.

For more information, see Specify Data Types Using Data Type Assistant.

Dependencies

To enable this parameter, click the Show data type assistant button.

Data type override — Specify data type override mode for this signal

Inherit | Off

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.

Signedness — Specify signed or unsigned

Signed (default) | Unsigned

Specify whether the fixed-point data is signed or unsigned. Signed data can represent positive and negative values, but unsigned data represents positive values only.

• Signed, specifies the fixed-point data as signed.

• Unsigned, specifies the fixed-point data as unsigned.

For more information, see Specify Data Types Using Data Type Assistant.

Dependencies

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

Word length — Bit size of the word that holds the quantized integer

16 (default) | integer from 0 to 32

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.

Scaling — Method for scaling your fixed-point data

Integer (default)

Specify the method for scaling your fixed-point data to avoid overflow conditions and minimize quantization errors. Selecting Integer specifies a binary point location for fixed-point data and sets the fraction length to 0. For more information, see Specify Data Types Using Data Type Assistant.

Dependencies

To enable this parameter, set Mode to Fixed point.

Block Characteristics

Data Types	Boolean | double | fixed point | integer | single
Direct Feedthrough	yes
Multidimensional Signals	yes
Variable-Size Signals	yes
Zero-Crossing Detection	no

Extended Capabilities

C/C++ Code Generation
Generate C and C++ code using Simulink® Coder™.

Fixed-Point Conversion
Design and simulate fixed-point systems using Fixed-Point Designer™.

Version History

Introduced in R2010a