Struct Formula 

pub struct Formula {
    pub dependent: String,
    pub independents: Vec<String>,
    pub intercept: bool,
}

Represents a parsed formula in the form “y ~ x1 + x2 + … + xn”

Interaction Terms (v0.3.0)

• x1 * x2 : Full interaction (expands to x1 + x2 + x1:x2)
• x1 : x2 : Only the interaction term (x1 × x2)

Categorical Variables (NEW in v0.4.0)

• C(var) : Categorical encoding (creates dummies, drops first level)

Polynomial Terms (NEW in v0.4.0)

• I(x^2) : Polynomial terms (e.g., squared, cubed)

Fields

dependent: String

Name of the dependent variable (left-hand side)

independents: Vec<String>

Names of independent variables (right-hand side) May include:

• Regular variables: “x1”
• Interactions: “x1:x2”
• Categorical: “C(region)”
• Polynomials: “I(x^2)”

intercept: bool

Whether to include an intercept (default: true)

Implementations

impl Formula

pub fn parse(formula: &str) -> Result<Formula, GreenersError>

Parse a formula string in the R/Python style: “y ~ x1 + x2 + x3”

Syntax

• Basic: “y ~ x1 + x2 + x3” (with intercept)
• No intercept: “y ~ x1 + x2 + x3 - 1” or “y ~ 0 + x1 + x2”
• Intercept only: “y ~ 1”
• Full interaction: “y ~ x1 * x2” (expands to x1 + x2 + x1:x2)
• Interaction only: “y ~ x1 : x2” (only the interaction term)
• Categorical: “y ~ C(region)” (creates dummies)
• Polynomial: “y ~ I(x^2)” or “y ~ I(x**2)” (power terms)

Examples

use greeners_core::formula::Formula;

let f = Formula::parse("fte ~ tratado + t + effect").unwrap();
assert_eq!(f.dependent, "fte");
assert_eq!(f.independents, vec!["tratado", "t", "effect"]);
assert_eq!(f.intercept, true);

let f2 = Formula::parse("y ~ x1 + x2 - 1").unwrap();
assert_eq!(f2.intercept, false);

pub fn n_cols(&self) -> usize

Get the total number of columns in the design matrix (including intercept if present)

Trait Implementations

impl Clone for Formula

fn clone(&self) -> Formula

Returns a duplicate of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl Debug for Formula

fn fmt(&self, f: &mut Formatter<'_>) -> Result<(), Error>

Formats the value using the given formatter.