pint.models.parameter.Parameter

class pint.models.parameter.Parameter(name=None, value=None, units=None, description=None, uncertainty=None, frozen=True, aliases=None, continuous=True, prior=<pint.models.priors.Prior object>, use_alias=None, parent=None)

Bases: object

A single timing model parameter.

Subclasses of this class can represent parameters of various types. They can record units, a description of the parameter’s meaning, a default value in some cases, whether the parameter has ever been set, and they can keep track of whether a parameter is to be fit or not.

Parameters can also come in families, either in the form of numbered prefixParameter or with associated selection criteria in the form of maskParameter.

A parameter’s current value will be stored at .quantity, which will have associated units (astropy.quantity.Quantity) or other special type machinery, or can also be accessed through .value, which provides the raw value (stripped of units if applicable). Both of these can be assigned to to change the parameter’s value. If the parameter has units, they will be accessible through the .units property (an astropy.units.Unit). A parameter that has not been set will have the value None.

Parameters also support uncertainties; these are available including units through the .uncertainty attribute. Parameters can also be set as .frozen=True to indicate that they should not be modified as part of a fit.

Parameters:

• name (str, optional) – The name of the parameter.

• value (number, str, astropy.units.Quantity, or other data type or object) – The input parameter value. Quantities are accepted here, but when the corresponding property is read the value will never have units.

• units (str or astropy.units.Unit, optional) – Parameter default unit. Parameter .value and .uncertainty_value attribute will associate with the default units.

• description (str, optional) – A short description of what this parameter means.

• uncertainty (float) – Current uncertainty of the value.

• frozen (bool, optional) – A flag specifying whether Fitter objects should adjust the value of this parameter or leave it fixed.

• aliases (list, optional) – An optional list of strings specifying alternate names that can also be accepted for this parameter.

• continuous (bool, optional) – A flag specifying whether derivatives with respect to this parameter exist.

• use_alias (str or None) – Alias to use on write; normally whatever alias was in the par file it was read from

• parent (pint.models.timing_model.Component, optional) – The parent timing model component

Variables:

quantity (astropy.units.Quantity or astropy.time.Time or bool or int) – The parameter’s value

Methods

add_alias(alias)	Add a name to the list of aliases for this parameter.
as_latex()
as_parfile_line([format])	Return a parfile line giving the current state of the parameter.
from_parfile_line(line)	Parse a parfile line into the current state of the parameter.
help_line()	Return a help line containing parameter name, description and units.
name_matches(name)	Whether or not the parameter name matches the provided name
prior_pdf([value, logpdf])	Return the prior probability density.
set(value)	Deprecated - just assign to .value.
str_quantity(quan)	Format the argument in an appropriate way as a string.
value_as_latex()

Attributes

prior	prior distribution for this parameter.
quantity	Value including units (if appropriate).
repeatable
uncertainty	Parameter uncertainty value with units.
uncertainty_value	Return a pure value from .uncertainty.
units	Units associated with this parameter.
value	Return the value (without units) of a parameter.

property quantity

Value including units (if appropriate).

property value

Return the value (without units) of a parameter.

This value is assumed to be in units of self.units. Upon setting, a a Quantity can be provided, which will be converted to self.units.

property units

Units associated with this parameter.

Should be a astropy.units.Unit object, or None if never set.

property uncertainty

Parameter uncertainty value with units.

property uncertainty_value

Return a pure value from .uncertainty.

This will be interpreted as having units self.units.

property prior

prior distribution for this parameter.

This should be a Prior object describing the prior distribution of the quantity, for use in Bayesian fitting.

prior_pdf(value=None, logpdf=False)

Return the prior probability density.

Evaluated at the current value of the parameter, or at a proposed value.

Parameters:

• value (array-like or float, optional) – Where to evaluate the priors; should be a unitless number. If not provided the prior is evaluated at self.value.

• logpdf (bool) – If True, return the logarithm of the PDF instead of the PDF; this can help with densities too small to represent in floating-point.

str_quantity(quan)

Format the argument in an appropriate way as a string.

help_line()

Return a help line containing parameter name, description and units.

as_parfile_line(format='pint')

Return a parfile line giving the current state of the parameter.

Parameters:

format (str, optional) – Parfile output format. PINT outputs in ‘tempo’, ‘tempo2’ and ‘pint’ formats. The default format is pint.

Return type:

str

Notes

Format differences between tempo, tempo2, and pint at [1]

[1]

https://github.com/nanograv/PINT/wiki/PINT-vs.-TEMPO%282%29-par-file-changes

from_parfile_line(line)

Parse a parfile line into the current state of the parameter.

Returns True if line was successfully parsed, False otherwise.

Note

The accepted formats:

• NAME value

• NAME value fit_flag

• NAME value fit_flag uncertainty

• NAME value uncertainty

add_alias(alias)

Add a name to the list of aliases for this parameter.

name_matches(name)

Whether or not the parameter name matches the provided name

set(value)

Deprecated - just assign to .value.