System Identification Toolbox™

poly1d

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

Syntax

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

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.

Use poly1d to define a nonlinear function , where F is a single-variable polynomial function of x:

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 Name Description

Property Name	Description
`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.

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.

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 for the property 'Degree'.