Struct LabelEncoder 

pub struct LabelEncoder;

An unfitted label encoder.

Calling Fit::fit on an Array1<String> learns an alphabetically ordered mapping from unique string labels to integer indices 0, 1, ..., n_classes - 1 and returns a FittedLabelEncoder.

Examples

use ferrolearn_preprocess::LabelEncoder;
use ferrolearn_core::traits::{Fit, Transform};
use ndarray::array;

let enc = LabelEncoder::new();
let labels = array!["cat".to_string(), "dog".to_string(), "cat".to_string()];
let fitted = enc.fit(&labels, &()).unwrap();
let encoded = fitted.transform(&labels).unwrap();
assert_eq!(encoded[0], 0); // "cat" → 0
assert_eq!(encoded[1], 1); // "dog" → 1

Implementations

impl LabelEncoder

pub fn new() -> Self

Create a new LabelEncoder.

Trait Implementations

impl Clone for LabelEncoder

fn clone(&self) -> LabelEncoder

Returns a duplicate of the value.

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

Performs copy-assignment from source.

impl Debug for LabelEncoder

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

Formats the value using the given formatter.

impl Default for LabelEncoder

fn default() -> LabelEncoder

Returns the “default value” for a type.

impl Fit<ArrayBase<OwnedRepr<String>, Dim<[usize; 1]>>, ()> for LabelEncoder

fn fit( &self, x: &Array1<String>, _y: &(), ) -> Result<FittedLabelEncoder, FerroError>

Fit the encoder by learning the sorted set of unique labels.

Labels are sorted alphabetically; the first label maps to 0.

Errors

Returns FerroError::InsufficientSamples if the input is empty.

type Fitted = FittedLabelEncoder

The fitted model type returned by fit.

type Error = FerroError

The error type returned by fit.

impl FitTransform<ArrayBase<OwnedRepr<String>, Dim<[usize; 1]>>> for LabelEncoder

fn fit_transform(&self, x: &Array1<String>) -> Result<Array1<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; 1]>>> for LabelEncoder

Implement Transform on the unfitted encoder to satisfy the FitTransform: Transform supertrait bound. Calling transform on an unfitted encoder always returns an error.

fn transform(&self, _x: &Array1<String>) -> Result<Array1<usize>, FerroError>

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

Use Fit::fit to produce a FittedLabelEncoder, then call Transform::transform on that.

type Output = ArrayBase<OwnedRepr<usize>, Dim<[usize; 1]>>

The transformed output type.

type Error = FerroError

The error type returned by transform.