# idPolynomial1D

Class representing single-variable polynomial nonlinear estimator for Hammerstein-Wiener models

## Syntax

t=idPolynomial1D('Degree',n)
t=idPolynomial1D('Coefficients',C)
t=idPolynomial1D(n)

## Description

idPolynomial1D is an object that stores the single-variable polynomial nonlinear estimator for Hammerstein-Wiener models.

You can use the constructor to create the nonlinearity object, as follows:

t=idPolynomial1D('Degree',n) creates a polynomial nonlinearity estimator object of nth degree.

t=idPolynomial1D('Coefficients',C) creates a polynomial nonlinearity estimator object with coefficients C.

t=idPolynomial1D(n) a polynomial nonlinearity estimator object of nth degree.

Use evaluate(p,x) to compute the value of the function defined by the idPolynomial1D object p at x.

## idPolynomial1D Properties

After creating the object, you can use get or dot notation to access the object property values. For example:

% List all property values
get(p)
% Get value of Coefficients property
p.Coefficients
Property NameDescription
Degree

Positive integer specifies the degree of the polynomial
Default=1.

For example:

idPolynomial1D('Degree',3)
Coefficients

1-by-(n+1) matrix containing the polynomial coefficients.

FreeOption to fix or free the values in the mapping object. When you set Free to false, the object does not update during estimation.

## Examples

Use idPolynomial1D to specify the single-variable polynomial nonlinearity estimator in Hammerstein-Wiener models. For example:

m=nlhw(Data,Orders,idPolynomial1D('deg',3),[]);

where 'deg' is an abbreviation for the property 'Degree'.

## Tips

Use idPolynomial1D to define a nonlinear function $y=F\left(x\right)$, where F is a single-variable polynomial function of x:

$F\left(x\right)=c\left(1\right){x}^{n}+c\left(2\right){x}^{\left(n-1\right)}+\dots +c\left(n\right)x+c\left(n+1\right)$

## Version History

Introduced in R2007b

expand all

Not recommended starting in R2021b