Struct ColumnTransformer 

pub struct ColumnTransformer { /* private fields */ }

An unfitted column transformer.

Applies each registered transformer to its designated column subset, then horizontally concatenates all outputs. The Remainder policy controls what happens to columns not covered by any transformer.

Transformer order

Transformers are applied and their outputs concatenated in the order they were registered. Remainder columns (when remainder = Remainder::Passthrough) are appended last.

Overlapping selections

Each transformer receives its own copy of the selected columns, so overlapping ColumnSelectors are fully supported.

Examples

use ferrolearn_preprocess::column_transformer::{
    ColumnSelector, ColumnTransformer, Remainder,
};
use ferrolearn_preprocess::StandardScaler;
use ferrolearn_core::Fit;
use ferrolearn_core::Transform;
use ndarray::array;

let x = array![[1.0_f64, 10.0, 100.0], [2.0, 20.0, 200.0], [3.0, 30.0, 300.0]];
let ct = ColumnTransformer::new(
    vec![("scaler".into(), Box::new(StandardScaler::<f64>::new()), ColumnSelector::Indices(vec![0, 1]))],
    Remainder::Passthrough,
);
let fitted = ct.fit(&x, &()).unwrap();
let out = fitted.transform(&x).unwrap();
// 2 scaled columns + 1 passthrough column
assert_eq!(out.ncols(), 3);

Implementations

impl ColumnTransformer

pub fn new( transformers: Vec<(String, Box<dyn PipelineTransformer<f64>>, ColumnSelector)>, remainder: Remainder, ) -> Self

Create a new ColumnTransformer.

Parameters

• transformers: A list of (name, transformer, selector) triples.
• remainder: Policy for uncovered columns (Drop or Passthrough).

Trait Implementations

impl Fit<ArrayBase<OwnedRepr<f64>, Dim<[usize; 2]>>, ()> for ColumnTransformer

fn fit( &self, x: &Array2<f64>, _y: &(), ) -> Result<FittedColumnTransformer, FerroError>

Fit each transformer on its selected column subset.

Validates that all selected column indices are within bounds before fitting any transformer.

Errors

• FerroError::InvalidParameter if any column index is out of range.
• Propagates any error returned by an individual transformer’s fit_pipeline call.

type Fitted = FittedColumnTransformer

The fitted model type returned by fit.

type Error = FerroError

The error type returned by fit.

impl PipelineTransformer<f64> for ColumnTransformer

fn fit_pipeline( &self, x: &Array2<f64>, _y: &Array1<f64>, ) -> Result<Box<dyn FittedPipelineTransformer<f64>>, FerroError>

Fit the column transformer using the pipeline interface.

The y argument is ignored; it exists only for API compatibility.

Errors

Propagates errors from Fit::fit.