ml-data-pipeline

npm install @ferrow/ml-data-pipeline

Lightweight tabular data prep — no tensor/ML framework dependency. Column typing, normalization, one-hot encoding, seeded shuffling, splitting, and imputation, all built around a fit/transform split: params are computed once on training data and then replayed on other data, so you can't accidentally leak test-set statistics into your features.

What this is

• inferColumnTypes(data) — numeric vs categorical, per column.
• fitMinMax / applyMinMax and fitZScore / applyZScore — normalization and standardization, each split into a fit step (computes params from data) and an apply step (uses SAVED params — never recomputed from whatever data you pass it).
• fitOneHot / applyOneHot — one-hot encoding with an explicit unseen- category policy: 'ignore' (all-zero row), 'error' (throws), or 'extra-column' (<column>_unknown).
• mulberry32(seed) — a small seeded PRNG; seededShuffle(data, seed) — deterministic Fisher-Yates shuffle built on it.
• trainTestSplit(data, ratio, seed) — seeded shuffle-then-slice.
• fitImpute / applyImpute — mean / mode / constant imputation, same fit/apply split.
• Pipeline — chains steps (.impute(), .minmax(), .zscore(), .onehot()), .fit(train) computes and stores every step's params, .transform(anyData) replays those saved params, and .toJSON() / Pipeline.fromJSON() serialize/restore the fitted state.

What this is NOT

• No tensors, no GPU, no model training — this is preprocessing only.
• No CSV/file I/O — bring your own parsed Row[] (Record<string, string | number | null>).
• No image/text feature extraction — tabular columns only.

Quickstart

npm install
npm run build
node dist/examples/demo.js

API

import { Pipeline, trainTestSplit } from 'ml-data-pipeline';

const { train, test } = trainTestSplit(data, 0.75, 7); // seed=7, deterministic

const pipeline = new Pipeline().minmax('age');
pipeline.fit(train);              // computes min/max from TRAIN only
const testOut = pipeline.transform(test); // applies TRAIN's min/max to test

const saved = pipeline.toJSON();
const restored = Pipeline.fromJSON(saved);

Demo: proving no leakage

examples/demo.ts fits a min-max scaler on the train split, transforms the test split, and shows the test output matches a manual calculation done with only the train min/max — never test's own range:

$ node dist/examples/demo.js
train ages: [60, 80, 30, 40, 50, 70]  (min=30, max=80)
test raw ages: [90, 20]
test normalized (via pipeline): [1.2, -0.2]
matches manual TRAIN-param calc: true

Note the test values fall outside [0, 1] — expected, since they're scaled by the training range, not their own.

License

MIT

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Sponsored by Ferrow

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Part of the ferrow-toolkit collection · Sponsored by Ferrow