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dsp.MovingMaximum

Moving maximum

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Description

The dsp.MovingMaximum System object™ determines the moving maximum of the input signal along each channel, independently over time. The object uses the sliding window method to determine the moving maximum. In this method, a window of specified length is moved over each channel, sample by sample, and the object determines the maximum of the data in the window. For more details, see Algorithms.

The dsp.MovingMaximum object and the movmax function both compute the moving maximum of the input signal. However, the object can process large streams of real-time data and handle system states automatically. The function performs one-time computations on data that is readily available and cannot handle system states. For a comparison between the two, see System Objects vs MATLAB Functions.

To determine the moving maximum of the input:

  1. Create the dsp.MovingMaximum object and set its properties.

  2. Call the object with arguments, as if it were a function.

To learn more about how System objects work, see What Are System Objects?

Creation

Syntax

movMax = dsp.MovingMaximum
movMax = dsp.MovingMaximum(Len)
movMax = dsp.MovingMaximum(Name,Value)

Description

movMax = dsp.MovingMaximum returns a moving maximum object, movMax, using the default properties.

movMax = dsp.MovingMaximum(Len) sets the WindowLength property to Len.

example

movMax = dsp.MovingMaximum(Name,Value) specifies additional properties using Name,Value pairs. Unspecified properties have default values.

Example: movMax = dsp.MovingMaximum('SpecifyWindowLength',1,'WindowLength',10);

Properties

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Unless otherwise indicated, properties are nontunable, which means you cannot change their values after calling the object. Objects lock when you call them, and the release function unlocks them.

If a property is tunable, you can change its value at any time.

For more information on changing property values, see System Design in MATLAB Using System Objects.

Flag to specify a window length, specified as a scalar boolean.

  • true — The length of the sliding window is equal to the value you specify in the WindowLength property.

  • false — The length of the sliding window is infinite. In this mode, the object determines the maximum of the current sample and all the past samples.

Length of the sliding window in samples, specified as a positive scalar integer.

Dependencies

This property applies when you set SpecifyWindowLength to true.

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

Usage

Syntax

y = movMax(x)

Description

y = movMax(x) determines the moving maximum of the input signal, x, using the sliding window method.

example

Input Arguments

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Data input, specified as a vector or a matrix. If x is a matrix, each column is treated as an independent channel. The moving maximum is determined along each channel. The object also accepts variable-size inputs. Once the object is locked, you can change the size of each input channel, but you cannot change the number of channels.

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

Output Arguments

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Moving maximum of the input signal, returned as a vector or a matrix.

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

Object Functions

To use an object function, specify the System object as the first input argument. For example, to release system resources of a System object named obj, use this syntax:

release(obj)

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stepRun System object algorithm
releaseRelease resources and allow changes to System object property values and input characteristics
resetReset internal states of System object

Examples

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Open Script

Compute the moving maximum of a sum of three sine waves with varying amplitude. Use a sliding window of length 30.

Initialization

Set up an input signal that is a sum of three sine waves with frequencies at 2 Hz, 5 Hz, and 10 Hz. The sampling frequency is 100 Hz. Create a dsp.MovingMaximum object with a window length of 30. Create a time scope for viewing the output.

sin = dsp.SineWave('SampleRate',100,...
    'Frequency',[2 5 10],...
    'SamplesPerFrame',100);
movMax = dsp.MovingMaximum(30);
scope  = timescope('SampleRate',100,...
    'TimeSpanOverrunAction','Scroll',...
    'TimeSpanSource','Property',...
    'TimeSpan',10,'ShowGrid',true,...
    'YLimits',[-4.5 4.5]);

Compute the Moving Maximum

Each sine wave component of the input signal has a different amplitude that varies with the iteration. Use the movMax object to determine the maximum value of the current sample and the past 29 samples of the input signal.

for index = 1:100
    sin.Amplitude = rand(1,3);
    x = sum(sin(),2);
    xmax = movMax(x);
    scope([x,xmax])
end

Algorithms

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References

[1] Bodenham, Dean. “Adaptive Filtering and Change Detection for Streaming Data.” PH.D. Thesis. Imperial College, London, 2012.

Extended Capabilities

Version History

Introduced in R2016b

See Also

Functions

Objects

Blocks

Topics