rastro-analysis

Pure functions turning UX telemetry into user flows, for Rastro.

⚠️ Pre-alpha. APIs and the ux.* conventions will change.

No I/O, no framework, no clock. Fixture traces in, known output out — which is what makes the interesting part of the system testable.

Install

pnpm add rastro-analysis

Use

import { sessionize, buildGraph, detectFriction } from "rastro-analysis";

const sessions = sessionize(events);   // group by session.id, order by ux.seq
const graph = buildGraph(sessions);    // nodes, transitions, median dwell, drop-off
const friction = detectFriction(sessions);

sessionize groups events by session.id and orders each group by ux.seq — the sole authority for order. Timestamps are for display; user clocks are skewed and ordering by them scrambles sequences.

buildGraph aggregates sessions into a flow graph. count is how many sessions made a transition, so one user hammering a path can't outweigh a path many users take. medianMs is a median rather than a mean, because dwell is long-tailed and one walked-away-from-the-desk session would drag a mean somewhere meaningless.

detectFriction returns ranked deterministic signals — rage clicks and high-abandonment elements. Ranking uses sessions affected, the one measure comparable across signal kinds.

These are evidence, never a diagnosis. A rage click can be a slow network as easily as a confusing control; an exit point can be where the task legitimately finishes.

Works without the rest of Rastro

Anything conforming to the ux.* conventions can feed this. You don't need the SDK or the collector to use the analysis.

License

MIT © 2026 Andrew Schutt