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ComplexityMeasures.jl Dev Docs

Good practices in developing a code base apply in every Pull Request. The Good Scientific Code Workshop is worth checking out for this.

All PRs contributing new functionality must be well tested and well documented. You only need to add tests for methods that you explicitly extended.

Adding a new OutcomeSpace

Mandatory steps

  1. Decide on the outcome space and how the estimator will map probabilities to outcomes.
  2. Define your type and make it subtype OutcomeSpace.
  3. Add a docstring to your type following the style of the docstrings of other estimators.
  4. If suitable, the estimator may be able to operate based on Encodings. If so, it is preferred to implement an Encoding subtype and extend the methods encode and decode. This will allow your outcome space to be used with a larger span of entropy and complexity methods without additional effort. Have a look at the file defining OrdinalPatterns for an idea of how this works.

If your new outcome space is counting-based, then

  1. Implement dispatch for counts for your OutcomeSpace type. This method should return a Counts instance (just a wrapper around a DimArray). Follow existing implementations for guidelines, and ensure that the outcomes are the dimension labels on the array. You'll then get counts_and_outcomes for free.
  2. Implement dispatch for symbolize. This will ensure that the outcome space also works automatically with any discrete estimators in CausalityTools.jl.

If your new outcome space is not counting-based, then

  1. Implement dispatch for probabilities for your OutcomeSpace type. This method should return a Probabilities instance (also just a wrapper around DimArray with the constraint that the entries of the array must sum to 1). Follow existing implementations for guidelines, and ensure that the outcomes are the dimension labels on the probabilities array. You'll then get the methods probabilities_and_outcomes and outcomes for free.

Finally,

  1. Implement dispatch for outcome_space and your OutcomeSpace type. The return value of outcome_space must be sorted (as in the default behavior of sort, in ascending order).
  2. Add your outcome space type to the table list in the documentation page of outcome space. If you made an encoding, also add it to corresponding table in the encodings section.

Optional steps

The following methods may be extended for your OutcomeSpace if doing so leads to performance benefits.

  1. total_outcomes. By default it returns the length of outcome_space. This is the function that most typically has performance benefits if implemented explicitly, so most existing estimators extend it by default.

Adding a new ProbabilitiesEstimator

Mandatory steps

  1. Define your type and make it subtype ProbabilitiesEstimator.
  2. Add a docstring to your type following the style of the docstrings of other ProbabilitiesEstimators.
  3. Implement dispatch for probabilities for your ProbabilitiesEstimator type. You'll then get probabilities_and_outcomes for free.
  4. Implement dispatch for allprobabilities for your ProbabilitiesEstimator type. You'll then get allprobabilities_and_outcomes for free.
  5. Add your new ProbabilitiesEstimator type to the list of probabilities estimators in the probabilities estimators documentation section.

Adding a new InformationMeasureEstimator

The type implementation should follow the declared API of InformationMeasureEstimator. If the type is a discrete measure, then extend information(e::YourType, p::Probabilities). If it is a differential measure, then extend information(e::YourType, x::InputData).

ComplexityMeasures.InformationMeasureEstimator — Type
InformationMeasureEstimator{I <: InformationMeasure}

The supertype of all information measure estimators. Its direct subtypes are DiscreteInfoEstimator and DifferentialInfoEstimator.

Since all estimators must reference a measure definition in some way, we made the following interface decisions:

  1. all estimators have as first type parameter I <: InformationMeasure
  2. all estimators reference the information measure in a definition field
  3. all estimators are defined using Base.@kwdef so that they may be initialized with the syntax Estimator(; definition = Shannon()) (or any other).

Any concrete subtypes must follow the above, e.g.:

Base.@kwdef struct MyEstimator{I <: InformationMeasure, X} <: DiscreteInfoEstimator{I}
    definition::I
    x::X
end
Why separate the *definition* of a measure from *estimators* of a measure?

In real applications, we generally don't have access to the underlying probability mass functions or densities required to compute the various entropy or extropy definitons. Therefore, these information measures must be estimated from finite data. Estimating a particular measure (e.g. Shannon entropy) can be done in many ways, each with its own own pros and cons. We aim to provide a complete library of literature estimators of the various information measures (PRs are welcome!).

source

Adding a new InformationMeasure

This amounts to adding a new definition of an information measure, not an estimator. It de-facto means adding a method for the discrete Plug-In estimator.

Mandatory steps

  1. Define your information measure definition type and make it subtype InformationMeasure.
  2. Implement dispatch for information(def::YourType, p::Probabilities). This is the Plug-In estimator for the discrete measure.
  3. Add a docstring to your type following the style of the docstrings of other information measure definitions, and should include the mathematical definition of the measure.
  4. Add your information measure definition type to the list of definitions in the docs/src/information_measures.md documentation page.
  5. Add a reference to your information measure definition in the docstring for InformationMeasure.

Optional steps

  1. If the maximum value of your information measure type is analytically computable for a probability distribution with a known number of elements, implementing dispatch for information_maximum automatically enables information_normalized for your type.