autofit.LogUniformPrior#

class LogUniformPrior[source]#

Bases: Prior

A prior with a log base 10 uniform distribution, defined between a lower limit and upper limit.

The conversion of an input unit value, u, to a physical value, p, via the prior is as follows:

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For example for prior = LogUniformPrior(lower_limit=10.0, upper_limit=1000.0), an input prior.value_for(unit=0.5) is equal to 100.0.

[Rich describe how this is done via message]

Parameters:

lower_limit (float) – The lower limit of the log10 uniform distribution defining the prior.
upper_limit (float) – The upper limit of the log10 uniform distribution defining the prior.

Examples

prior = af.LogUniformPrior(lower_limit=0.0, upper_limit=2.0)

physical_value = prior.value_for(unit=0.2)

Methods

`assert_within_limits`
`dict`	A dictionary representation of this prior
`for_class_and_attribute_name`
`from_dict`	Returns a prior from a JSON representation.
`gaussian_prior_model_for_arguments`
`has`	Does this instance have an attribute which is of type cls?
`instance_for_arguments`
`log_prior_from_value`	Returns the log prior of a physical value, so the log likelihood of a model evaluation can be converted to a posterior as log_prior + log_likelihood.
`make_indexes`
`name_of_class`	A string name for the class, with the prior suffix removed.
`new`	Returns a copy of this prior with a new id assigned making it distinct
`next_id`
`project`
`random`	A random value sampled from this prior
`replacing_for_path`	Create a new model replacing the value for a given path with a new value
`tree_unflatten`	Create a prior from a flattened PyTree
`unit_value_for`	Compute the unit value between 0 and 1 for the physical value.
`value_for`	Returns a physical value from an input unit value according to the limits of the log10 uniform prior.
`with_limits`	Create a new log 10 uniform prior centred between two limits with sigma distance between this limits.
`with_message`

Attributes

`component_number`
`factor`	A callable PDF used as a factor in factor graphs
`identifier`
`label`
`limits`
`lower_unit_limit`	The lower limit for this prior in unit vector space
`ndim`	How many dimensions does this variable have?
`parameter_string`
`upper_unit_limit`	The upper limit for this prior in unit vector space
`width`

classmethod with_limits(lower_limit, upper_limit)[source]#

Create a new log 10 uniform prior centred between two limits with sigma distance between this limits.

Note that these limits are not strict so exceptions will not be raised for values outside of the limits.

This function is typically used in prior passing, where the result of a model-fit are used to create new Gaussian priors centred on the previously estimated median PDF model.

Parameters:

lower_limit (float) – The lower limit of the new LogUniform prior.
upper_limit (float) – The upper limit of the new LogUniform Prior.

Return type:

A new LogUniform.

log_prior_from_value(value)[source]#

Returns the log prior of a physical value, so the log likelihood of a model evaluation can be converted to a posterior as log_prior + log_likelihood.

This is used by certain non-linear searches (e.g. Emcee) in the log likelihood function evaluation.

Parameters:: value (float) – The physical value of this prior’s corresponding parameter in a NonLinearSearch sample.
Return type:: float

value_for(unit, ignore_prior_limits=False)[source]#

Returns a physical value from an input unit value according to the limits of the log10 uniform prior.

Parameters:: unit (float) – A unit value between 0 and 1.
Returns:: The unit value mapped to a physical value according to the prior.
Return type:: value

Examples

prior = af.LogUniformPrior(lower_limit=0.0, upper_limit=2.0)

physical_value = prior.value_for(unit=0.2)