# Model¶

class sherpa.models.model.Model(name, pars=())[source] [edit on github]

The base class for Sherpa models.

A model contains zero or more parameters that control the predictions of the model when given one or more coordinates. These parameters may represent some variable that describes the model, such as the temperature of a black body, or the computation, such as what form of interpolation to use.

Parameters
• name (str) – A label for the model instance.

• pars (sequence of sherpa.parameter.Parameter objects) – The parameters of the model.

name

The name given to the instance.

Type

str

pars

The parameters of the model instance.

Type

tuple of sherpa.parameter.Parameter objects

Notes

Parameters can be accessed via the pars attribute, but it is expected that they will generally be accessed directly, as the class provides case-insensitive access to the parameter names as object attributes. That is, if the model contains parameters called breakFreq and norm, and the instance is stored in the variable mdl, then the following can be used to access the parameters:

print("Break frequency = {}".format(mdl.breakfreq))

mdl.norm = 1.2e-3


Attributes Summary

 ndim The dimensionality of the model, if defined, or None. thawedparhardmaxes The hard maximum values for the thawed parameters. thawedparhardmins The hard minimum values for the thawed parameters. thawedparmaxes Access to the maximum limits for the thawed parameters thawedparmins Access to the minimum limits for the thawed parameters thawedpars Access to the thawed parameters of the model

Methods Summary

 calc(p, *args, **kwargs) Evaluate the model on a grid. guess(dep, *args, **kwargs) Set an initial guess for the parameter values. Reset the parameter values. set_center(*args, **kwargs) startup([cache]) Called before a model may be evaluated multiple times. Called after a model may be evaluated multiple times.

Attributes Documentation

ndim = None

The dimensionality of the model, if defined, or None.

thawedparhardmaxes

The hard maximum values for the thawed parameters.

thawedparhardmins

The hard minimum values for the thawed parameters.

thawedparmaxes

thawedparmins

thawedpars

Methods Documentation

calc(p, *args, **kwargs)[source] [edit on github]

Evaluate the model on a grid.

Parameters
• p (sequence of numbers) – The parameter values to use. The order matches the pars field.

• *args – The model grid. The values can be scalar or arrays, and the number depends on the dimensionality of the model and whether it is being evaluated over an integrated grid or at a point (or points).

get_center()[source] [edit on github]
guess(dep, *args, **kwargs)[source] [edit on github]

Set an initial guess for the parameter values.

Attempt to set the parameter values, and ranges, for the model to match the data values. This is intended as a rough guess, so it is expected that the model is only evaluated a small number of times, if at all.

reset()[source] [edit on github]

Reset the parameter values.

set_center(*args, **kwargs)[source] [edit on github]
startup(cache=False)[source] [edit on github]

Called before a model may be evaluated multiple times.

Parameters

cache (bool, optional) – Should a cache be used when evaluating the models.

teardown()[source] [edit on github]

Called after a model may be evaluated multiple times.

setup()