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# poly1d

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

## Syntax

t=poly1d('Degree',n)
t=poly1d('Coefficients',C)
t=poly1d(n)

## Description

poly1d 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=poly1d('Degree',n) creates a polynomial nonlinearity estimator object of nth degree.

t=poly1d('Coefficients',C) creates a polynomial nonlinearity estimator object with coefficients C.

t=poly1d(n) a polynomial nonlinearity estimator object of nth degree.

Use evaluate(p,x) to compute the value of the function defined by the poly1d object p at x.

## poly1d 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:

`poly1d('Degree',3)`
Coefficients

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

## Examples

Use poly1s to specify the single-variable polynomial nonlinearity estimator in Hammerstein-Wiener models. For example:

`m=nlhw(Data,Orders,poly1d('deg',3),[]);`

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

Use poly1d to define a nonlinear function $y=F\left(x\right)$, where F is a single-variable polynomial function of x:
$F\left(x\right)=c\left(1\right){x}^{n}+c\left(2\right){x}^{\left(n-1\right)}+\dots +c\left(n\right)x+c\left(n+1\right)$