idUnitGain

Specify absence of nonlinearities for specific input or output channels in Hammerstein-Wiener models

Syntax

unit=idUnitGain


Description

unit=idUnitGain instantiates an object that specifies an identity mapping F(x)=x to exclude specific input and output channels from being affected by a nonlinearity in Hammerstein-Wiener models.

Use the idUnitGain object as an argument in the nlhw estimator to set the corresponding channel nonlinearity to unit gain.

For example, for a two-input and one-output model, to exclude the second input from being affected by a nonlinearity, use the following syntax:

m = nlhw(data,orders,['idSaturation''idUnitGain'],'idDeadZone')

In this case, the first input saturates and the output has an associated deadzone nonlinearity.

idUnitGain Properties

idUnitGain does not have properties.

Examples

For example, for a one-input and one-output model, to exclude the output from being affected by a nonlinearity, use the following syntax:

m = nlhw(Data,Orders,'idSaturation','idUnitGain')

In this case, the input has a saturation nonlinearity.

If nonlinearities are absent in input or output channels, you can replace idUnitGain with an empty matrix. For example, to specify a Wiener model with a sigmoid nonlinearity at the output and a unit gain at the input, use the following command:

m = nlhw(Data,Orders,[],'idSigmoidNetwork');

Tips

Use the idUnitGain object to exclude specific input and output channels from being affected by a nonlinearity in Hammerstein-Wiener models. idUnitGain is a linear function $$y=F(x)$$, where F(x)=x.

Version History

Introduced in R2007a

R2021b: Use of previous idnlarx and idnlhw mapping object names is not recommended.

Starting in R2021b, the mapping objects (also known as nonlinearities) used in the nonlinear components of the idnlarx and idnlhw objects have been renamed. The following table lists the name changes.

Pre-R2021b Name	R2021b Name
wavenet	idWaveletNetwork
sigmoidnet	idSigmoidNetwork
treepartition	idTreePartition
customnet	idCustomNetwork
saturation	idSaturation
deadzone	idDeadZone
pwlinear	idPiecewiseLinear
poly1d	idPolynomial1D
unitgain	idUnitGain
linear	idLinear
neuralnet	idFeedforwardNetwork

Scripts with the old names still run normally, although they will produce a warning. Consider using the new names for continuing compatibility with newly developed features and algorithms. There are no plans to exclude the use of these object names at this time.