Struct StandardScaler 

pub struct StandardScaler { /* private fields */ }

Online standard scaler that standardizes features to approximately zero mean and unit variance.

• When with_mean = false, the mean subtraction is skipped.
• When with_std = false, the scaling is skipped.
• When a feature has seen zero samples, its mean is 0 and scale is 1, so the original value is returned unchanged.
• When a feature’s variance is below epsilon, the scale is 1 to avoid NaN or Infinity.

transform does not update state; only update does.

Implementations

impl StandardScaler

pub fn new(feature_count: usize) -> Result<Self, RillError>

Create a new scaler for feature_count features with default config.

pub fn with_config( feature_count: usize, config: StandardScalerConfig, ) -> Result<Self, RillError>

Create a new scaler with a custom configuration.

pub fn means(&self) -> &[f64]

The per-feature means.

pub fn variances(&self) -> Vec<f64>

The per-feature variances (population).

pub fn std_devs(&self) -> Vec<f64>

The per-feature standard deviations.

pub fn scales(&self) -> Vec<f64>

The per-feature scales used during transformation.

pub fn validate(&self) -> Result<(), RillError>

Validate all configuration and persisted-state invariants.

This is run automatically during deserialization and before operations that index per-feature state. The hot path (transform_into / transform) relies on the invariants established here and by the private constructor, and only re-checks them under debug_assert!.

pub fn transform_into( &self, features: &[f64], output: &mut Vec<f64>, ) -> Result<(), RillError>

Transform features into the provided output buffer, reusing its allocation instead of allocating a fresh Vec on every call.

This is the hot-path entry point. Compared to transform it avoids two temporary allocations (the variances() and scales() vectors) by fusing the scale computation into the single output loop. The trust-boundary checks (dimension validation and finite-output enforcement) are preserved; the internal-state invariants established by validate and the private constructor are only re-checked under debug_assert! because they are guaranteed by the private fields and the validated deserialization path.

output is truncated to the feature count and then filled; callers that reuse the same buffer across iterations avoid allocation entirely after the first call.

Trait Implementations

impl Clone for StandardScaler

fn clone(&self) -> StandardScaler

Returns a duplicate of the value.

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

Performs copy-assignment from source.

impl Debug for StandardScaler

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

Formats the value using the given formatter.

impl Transformer for StandardScaler

fn input_dim(&self) -> usize

Expected number of input features.

fn output_dim(&self) -> usize

Number of features produced by transform.

fn transform(&self, features: &[f64]) -> Result<Vec<f64>, RillError>

Transform features using the current internal state.

fn update(&mut self, features: &[f64]) -> Result<(), RillError>

Update internal statistics using raw features.

fn samples_seen(&self) -> u64

How many samples the transformer has seen.

fn reset(&mut self)

Reset the transformer to its initial state.