API Reference

This reference provides detailed documentation for all modules, classes, and methods in the current release of formulae.

formulae

formulae.design_matrices(formula, data, na_action='drop', env=0, extra_namespace=None)

Parse model formula and obtain a DesignMatrices object containing objects representing the response and the design matrices for both the common and group specific effects.

Parameters

• formula (string) – A model formula.

• data (pandas.DataFrame) – The data frame where variables in the formula are taken from.

• na_action (string) – Describes what to do with missing values in data. "drop" means to drop all rows with a missing value, "error" means to raise an error, "pass" means to to keep all. Defaults to "drop".

• env (integer) – The number of environments we walk up in the stack starting from the function’s caller to capture the environment where formula is evaluated. Defaults to 0 which means the evaluation environment is the environment where design_matrices is called.

• extra_namespace (dict) – Additional user supplied transformations to include in the environment where the formula is evaluated. Defaults to None.

Returns

design – An instance of DesignMatrices that contains the design matrice(s) described by formula.

Return type

DesignMatrices

formulae.model_description(formula)

Interpret model formula and obtain a model description.

This function receives a string with a formula describing a statistical model and returns an object of class ModelTerms that describes the model interpreted from the formula.

Parameters

formula (string) – A string with a model description in formula language.

Return type

An object of class ModelTerms with an internal description of the model.

formulae.matrices

class formulae.matrices.DesignMatrices(model, data, env)

A wrapper of the response, the common, and group specific effects.

Parameters

• model (Model) – The model description, the result of calling model_description.

• data (pandas.DataFrame) – The data frame where variables are taken from.

• env (Environment) – The environment where values and functions are taken from.

response

The response in the model. Access its values with self.response.design_matrix. It is None if there is no response term in the model.

Type

ResponseMatrix

common

The common effects (a.k.a. fixed effects) in the model. The design matrix can be accessed with self.common.design_matrix. The submatrix for a term is accessed via self.common[term_name]. It is None if there are no common terms in the model.

Type

CommonEffectsMatrix

group

The group specific effects (a.k.a. random effects) in the model. The design matrix can be accessed with self.group.design_matrix. The submatrix for a term is accessed via self.group[term_name]. It is None if there are no group specific terms in the model.

Type

GroupEffectsMatrix