Struct OrdinalEncoder 

pub struct OrdinalEncoder;

An unfitted ordinal encoder.

Calling Fit::fit on an Array2<String> learns, for each column, a mapping from the unique string categories (in order of first appearance) to consecutive integers 0, 1, 2, ..., and returns a FittedOrdinalEncoder.

Examples

use ferrolearn_preprocess::ordinal_encoder::OrdinalEncoder;
use ferrolearn_core::traits::{Fit, Transform};
use ndarray::Array2;

let enc = OrdinalEncoder::new();
let data = Array2::from_shape_vec(
    (3, 2),
    vec![
        "cat".to_string(), "small".to_string(),
        "dog".to_string(), "large".to_string(),
        "cat".to_string(), "small".to_string(),
    ],
).unwrap();
let fitted = enc.fit(&data, &()).unwrap();
let encoded = fitted.transform(&data).unwrap();
assert_eq!(encoded[[0, 0]], 0); // "cat" is index 0 in col 0
assert_eq!(encoded[[1, 0]], 1); // "dog" is index 1 in col 0

Implementations

impl OrdinalEncoder

pub fn new() -> Self

Create a new OrdinalEncoder.

Trait Implementations

impl Clone for OrdinalEncoder

fn clone(&self) -> OrdinalEncoder

Returns a duplicate of the value.

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

Performs copy-assignment from source.

impl Debug for OrdinalEncoder

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

Formats the value using the given formatter.

impl Default for OrdinalEncoder

fn default() -> OrdinalEncoder

Returns the “default value” for a type.

impl Fit<ArrayBase<OwnedRepr<String>, Dim<[usize; 2]>>, ()> for OrdinalEncoder

fn fit( &self, x: &Array2<String>, _y: &(), ) -> Result<FittedOrdinalEncoder, FerroError>

Fit the encoder by building per-column category-to-index mappings.

Categories are recorded in order of first appearance in each column.

Errors

Returns FerroError::InsufficientSamples if the input has zero rows.

type Fitted = FittedOrdinalEncoder

The fitted model type returned by fit.

type Error = FerroError

The error type returned by fit.

impl FitTransform<ArrayBase<OwnedRepr<String>, Dim<[usize; 2]>>> for OrdinalEncoder

fn fit_transform(&self, x: &Array2<String>) -> Result<Array2<usize>, FerroError>

Fit the encoder on x and return the encoded output in one step.

Errors

Returns an error if fitting or transformation fails.

type FitError = FerroError

The error type for the combined fit-transform operation.

impl Transform<ArrayBase<OwnedRepr<String>, Dim<[usize; 2]>>> for OrdinalEncoder

Implement Transform on the unfitted encoder to satisfy the FitTransform: Transform supertrait bound.

fn transform(&self, _x: &Array2<String>) -> Result<Array2<usize>, FerroError>

Always returns an error — the encoder must be fitted first.

type Output = ArrayBase<OwnedRepr<usize>, Dim<[usize; 2]>>

The transformed output type.

type Error = FerroError

The error type returned by transform.