PowerLaw1D¶
-
class
astropy.modeling.powerlaws.
PowerLaw1D
(amplitude=1, x_0=1, alpha=1, **kwargs)[source]¶ Bases:
astropy.modeling.Fittable1DModel
One dimensional power law model.
- Parameters
amplitude : float
Model amplitude at the reference point
x_0 : float
Reference point
alpha : float
Power law index
- Other Parameters
fixed : a dict, optional
A dictionary
{parameter_name: boolean}
of parameters to not be varied during fitting. True means the parameter is held fixed. Alternatively thefixed
property of a parameter may be used.tied : dict, 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 thetied
property of a parameter may be used.bounds : dict, optional
eqcons : list, optional
A list of functions of length
n
such thateqcons[j](x0,*args) == 0.0
in a successfully optimized problem.ineqcons : list, optional
A list of functions of length
n
such thatieqcons[j](x0,*args) >= 0.0
is a successfully optimized problem.
Notes
Model formula (with \(A\) for
amplitude
and \(\alpha\) foralpha
):\[f(x) = A (x / x_0) ^ {-\alpha}\]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).Methods Summary
evaluate
(x, amplitude, x_0, alpha)One dimensional power law model function
fit_deriv
(x, amplitude, x_0, alpha)One dimensional power law derivative with respect to parameters
Attributes Documentation
-
alpha
= Parameter('alpha', value=1.0)¶
-
amplitude
= Parameter('amplitude', value=1.0)¶
-
input_units
¶ 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).Model sub-classes can also use function annotations in evaluate to indicate valid input units, in which case this property should not be overridden since it will return the input units based on the annotations.
-
param_names
= ('amplitude', 'x_0', 'alpha')¶
-
x_0
= Parameter('x_0', value=1.0)¶
Methods Documentation