Formula

A parsed model formula: the structured representation of a GAM’s right-hand side.

Usage

Source

Formula(
    response,
    terms,
    intercept=True,
)

A Formula is what whittaker.formula.parser.parse produces from a formula string such as "y ~ s(x1) + s(x2, bs='cr', k=15) + te(x3, x4) + group", and is what GAM.__init__ accepts either as that raw string or as an already-parsed Formula object. It separates the response column name from an ordered list of Term objects (LinearTerm, SmoothTerm, InteractionTerm, OffsetTerm) describing the right-hand side, plus whether an intercept is included. Downstream code (whittaker.model_matrix.build_model_matrix) consumes a Formula to construct the actual numeric design matrix and penalty structure used for fitting.

Parameters

response: str

Name of the response variable (the left-hand side, before ~).

terms: list[Term]

Ordered list of model terms (the right-hand side, after ~), where Term is a union of LinearTerm, SmoothTerm, InteractionTerm, and OffsetTerm.

intercept: bool = True

Whether the model includes an intercept column. True by default; suppress it by including 0 + or - 1 on the right-hand side of the formula string (e.g. "y ~ 0 + s(x)").

Methods

Name	Description
required_columns()	Return every data column name referenced by the formula, in first-seen order.

---

required_columns()

Return every data column name referenced by the formula, in first-seen order.

Usage

Source

required_columns()

Walks the response name and every term, collecting the response, each LinearTerm.variable, each SmoothTerm’s variables (and its by column, if any), and both sides of each InteractionTerm. OffsetTerm is skipped because its expression may be an arbitrary expression string rather than a bare column name. Names are deduplicated while preserving the order in which they were first encountered.

Returns

list of str

Column names that must be present in a data dictionary passed to ~whittaker.model_matrix.build_model_matrix.