dsp.RMS

(Removed) Root mean square of vector elements

The dsp.RMS System object™ has been removed. To compute the RMS, use the rms function. To compute the running RMS in MATLAB^®, use the dsp.MovingRMS object. For more information, see Compatibility Considerations.

Description

The dsp.RMS object computes the root mean square (RMS) value.

To compute the RMS value of your input:

1. Create the dsp.RMS 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

rms = dsp.RMS

rms = dsp.RMS(Name,Value)

Description

rms = dsp.RMS returns a System object, rms, that computes the root mean square (RMS) of an input or a sequence of inputs over the specified Dimension.

rms = dsp.RMS(Name,Value) returns an RMS System object, rms, with each specified property set to the specified value.

Properties

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.

RunningRMS — Enable calculating RMS over time

false (default) | true

Set this property to true to enable calculating the RMS over successive calls to the object algorithm.

ResetInputPort — Enable resetting in running RMS mode

false (default) | true

Set this property to true to enable resetting the running RMS. When the property is set to true, you must specify a reset input to the object algorithm to reset the running RMS.

Dependencies

This property applies when you set the RunningRMS property to true.

ResetCondition — Reset condition for running RMS mode

Non-zero (default) | Rising edge | Falling edge | Either edge

Specify the event to reset the running RMS as one of Rising edge, Falling edge, Either edge, or Non-zero. Non-zero resets the running RMS each time a nonzero sample is acquired. See Rising and Falling Edges for definitions of rising and falling edges.

Dependencies

This property applies when you set the ResetInputPort property to true.

Dimension — Dimension to compute RMS value along

Column (default) | All | Row | Custom

Specify the dimension along which to calculate the RMS as one of All, Row, Column, or Custom. Specifying the Dimension property as All computes the RMS value over the entire input.

Dependencies

This property applies only when you set the RunningRMS property to false.

CustomDimension — Numerical dimension to operate along

1 (default) | positive integer

Specify the dimension (one-based scalar integer value) of the input signal, along which the RMS is computed. The dimension cannot exceed the number of dimensions in the input signal.

Dependencies

This property applies when you set the Dimension property to Custom.

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

Usage

Syntax

y = rms(x)

y = rms(x,r)

Description

y = rms(x) computes the root mean square (RMS) output, y, of input vector x. When the RunningRMS property is true, y corresponds to the RMS of the input elements over successive calls to the object algorithm.

y = rms(x,r) resets the running RMS state based on the value of r, the reset signal, and the ResetCondition property. This computation is possible when you set both the RunningRMS and the ResetInputPort properties to true.

Input Arguments

x — Data input

vector | matrix

Data input, specified as a vector or a matrix. If x is a matrix, each column is treated as an independent channel. The RMS is computed along each channel. The object also accepts variable-size inputs. Once the object is locked, you can change the size of each input channel.

Data Types: single | double
Complex Number Support: Yes

r — Reset signal

scalar

Reset signal used to reset the running RMS, specified as a scalar value. The object resets the running RMS if the reset signal satisfies the ResetCondition.

Dependencies

To enable this signal, set the RunningRMS property to true and the ResetInputPort property to true.

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

Output Arguments

y — RMS output

scalar | vector | matrix

RMS output, returned as a scalar, vector or a matrix. If RunningRMS is set to:

• false –– The object computes the RMS value of each input channel. If the input is a column vector, the output is a scalar. If the input is a multichannel signal, the output signal is a 1-by-N vector, where N is the number of input channels.

• true –– The object computes the running RMS of the signal. The size of the output signal matches the size of the input signal.

Data Types: single | double
Complex Number Support: Yes

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)

Common to All System Objects

step	Run System object algorithm
release	Release resources and allow changes to System object property values and input characteristics
reset	Reset internal states of System object

Examples

RMS Value of Matrix Input

Note

If you are using R2016a or an earlier release, replace each call to the object with the equivalent step syntax. For example, obj(x) becomes step(obj,x).

Compute the RMS value of a matrix with the Dimension property set to 'All'.

in2 = magic(4);
rms2d = dsp.RMS;
rms2d.Dimension = 'All';
y_rms2 = rms2d(in2)

y_rms2 = 9.6695

The output is equivalent to reshaping the 4-by-4 matrix into a 16-by-1 or 1-by-16 vector and computing the RMS value for the vector.

More About

Root Mean Square Level

The root-mean-square level of a vector, X, is

$$x_{\text{RMS}}=\sqrt{\frac{1}{N}{\displaystyle \sum _{n=1}^N{\left|x_n\right|}^2}},$$

with the summation performed along the specified dimension.

Rising and Falling Edges

A rising edge:

• Rises from a negative value to a positive value or zero.

• Rises from zero to a positive value, where the rise is not a continuation of a rise from a negative value to zero.

A falling edge:

• Falls from a positive value to a negative value or zero.

• Falls from zero to a negative value, where the fall is not a continuation of a fall from a positive value to zero.

Algorithms

This object implements the algorithm, inputs, and outputs described on the RMS block reference page. The object properties correspond to the Simulink^® block parameters, except:

• The Treat sample-based row input as a column block parameter is not supported by the dsp.RMS object.

• The Reset Port block parameter corresponds to both the ResetCondition and the ResetInputPort object properties.

Compatibility Considerations

dsp.RMS System object has been removed

Errors starting in R2021a

The dsp.RMS System object has been removed. To compute the RMS, use the rms function. To compute the running RMS, use the dsp.MovingRMS object.

Update Code

This table shows typical usage of the System object and explains how to update existing code to use the equivalent function.

Discouraged Usage	Recommended Replacement
RMS rm = dsp.RMS; x = randn(100,1); y = rm(x); Running RMS rm = dsp.RMS; rm.RunningRMS = true; x = randn(100,1); % Running RMS y = rm(x); If you are using a release prior to R2016b, replace rm(x) with step(rm,x).	RMS x = randn(100,1); y = rms(x); Running RMS mvgRMS = dsp.MovingRMS; mvgRMS.SpecifyWindowLength = false; x = randn(100,1); y = mvgRMS(x);

Extended Capabilities

C/C++ Code Generation

Generate C and C++ code using MATLAB® Coder™.

Usage notes and limitations:

See System Objects in MATLAB Code Generation (MATLAB Coder).