class astropy.modeling.functional_models.Trapezoid1D(amplitude=1, x_0=0, width=1, slope=1, **kwargs)[source]#

Bases: Fittable1DModel

One dimensional Trapezoid model.


Amplitude of the trapezoid


Center position of the trapezoid


Width of the constant part of the trapezoid.


Slope of the tails of the trapezoid

Other Parameters:
fixeddict, optional

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.

tieddict, optional

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.

boundsdict, optional

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

eqconslist, optional

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

ineqconslist, optional

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


import numpy as np
import matplotlib.pyplot as plt

from astropy.modeling.models import Trapezoid1D

s1 = Trapezoid1D()
r = np.arange(-5, 5, .01)

for factor in range(1, 4):
    s1.amplitude = factor
    s1.width = factor
    plt.plot(r, s1(r), color=str(0.25 * factor), lw=2)

plt.axis([-5, 5, -1, 4])

(png, svg, pdf)


Attributes Summary



This property is used to indicate what units or sets of units the evaluate method expects, and returns a dictionary mapping inputs to units (or None if any units are accepted).


Names of the parameters that describe models of this type.




Methods Summary

evaluate(x, amplitude, x_0, width, slope)

One dimensional Trapezoid model function.

Attributes Documentation

amplitude = Parameter('amplitude', value=1.0)#
param_names = ('amplitude', 'x_0', 'width', 'slope')#

Names of the parameters that describe models of this type.

The parameters in this tuple are in the same order they should be passed in when initializing a model of a specific type. Some types of models, such as polynomial models, have a different number of parameters depending on some other property of the model, such as the degree.

When defining a custom model class the value of this attribute is automatically set by the Parameter attributes defined in the class body.

slope = Parameter('slope', value=1.0)#
width = Parameter('width', value=1.0)#
x_0 = Parameter('x_0', value=0.0)#

Methods Documentation

static evaluate(x, amplitude, x_0, width, slope)[source]#

One dimensional Trapezoid model function.