Chebyshev2D

class astropy.modeling.polynomial.Chebyshev2D

Bases: astropy.modeling.polynomial.OrthoPolynomialBase

2D Chebyshev polynomial of the 1st kind.

It is defined as

Parameters:

x_degree : int

degree in x

y_degree : int

degree in y

x_domain : list or None

domain of the x independent variable

y_domain : list or None

domain of the y independent variable

x_window : list or None

range of the x independent variable

y_window : list or None

range of the y independent variable

param_dim : int

number of parameter sets

**params : dict

keyword: value pairs, representing parameter_name: value

Other Parameters:  

fixed : a dict

A dictionary {parameter_name: boolean} of parameters to not be varied during fitting. True means the parameter is held fixed. Alternatively the fixed property of a parameter may be used.

tied : dict

A dictionary {parameter_name: callable} of parameters which are linked to some other parameter. The dictionary values are callables providing the linking relationship. Alternatively the tied property of a parameter may be used.

bounds : dict

A dictionary {parameter_name: boolean} of lower and upper bounds of parameters. Keys are parameter names. Values are a list of length 2 giving the desired range for the parameter. Alternatively the min and max properties of a parameter may be used.

eqcons : list

A list of functions of length n such that eqcons[j](x0,*args) == 0.0 in a successfully optimized problem.

ineqcons : list

A list of functions of length n such that ieqcons[j](x0,*args) >= 0.0 is a successfully optimized problem.

Methods Summary

fit_deriv(x, y, *params)

Derivatives with respect to the coefficients.

Methods Documentation

fit_deriv(x, y, *params)

Derivatives with respect to the coefficients.

This is an array with Chebyshev polynomials:

Parameters:

x : ndarray

input

y : ndarray

input

params : throw away parameter

parameter list returned by non-linear fitters

Returns:

result : ndarray

The Vandermonde matrix