tsb — Customer Cohorts

1 · Monthly signups & cumulative growth

Group raw signup events by their cohort month, then take a running total.

TypeScript

import { DataFrame, cumsum, pctChangeSeries, roundSeries } from "tsb";

const events = DataFrame.fromColumns({
  customer_id: Array.from({ length: 60 }, (_, i) => 1000 + i),
  signup_month: [
    ...Array(4).fill("2024-01"),
    ...Array(6).fill("2024-02"),
    ...Array(5).fill("2024-03"),
    ...Array(8).fill("2024-04"),
    ...Array(7).fill("2024-05"),
    ...Array(9).fill("2024-06"),
    ...Array(11).fill("2024-07"),
    ...Array(10).fill("2024-08"),
  ],
});

// .size() returns a Series with month → count
const sizeSer = events.groupby("signup_month").size();
const monthly = DataFrame.fromColumns({
  signup_month: [...sizeSer.index.values].map(String),
  signups: [...sizeSer.values].map(Number),
});
console.log("Signups per cohort month:");
console.log(monthly.toString());

const counts    = monthly.col("signups");
const cumulative = cumsum(counts);
const momPct     = roundSeries(pctChangeSeries(counts).mul(100), 1);

const out = monthly.assign({ cumulative, mom_growth_pct: momPct });
console.log("");
console.log(out.toString());

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2 · Visualise cohort growth

Bar chart of new customers per month.

TypeScript

import { DataFrame } from "tsb";

const monthly = DataFrame.fromColumns({
  month: ["Jan","Feb","Mar","Apr","May","Jun","Jul","Aug"],
  signups: [4, 6, 5, 8, 7, 9, 11, 10],
});

function bar(label: string, value: number, max: number, width = 28): string {
  const len = max > 0 ? Math.round((value / max) * width) : 0;
  return label.padEnd(14) + " | " + "\u2588".repeat(len) + " " + value.toFixed(2);
}
function chart(title: string, rows: Array<[string, number]>): void {
  const maxV = Math.max(...rows.map(r => r[1]));
  console.log(title);
  for (const [label, value] of rows) console.log(bar(label, value, maxV));
}

const monthsArr  = [...monthly.col("month").values].map(String);
const signupsArr = [...monthly.col("signups").values].map(Number);
const rows: Array<[string, number]> = monthsArr.map((m, i) => [m, signupsArr[i] as number]);
chart("New signups per month", rows);

const total = signupsArr.reduce((a, b) => a + b, 0);
const best  = monthsArr[signupsArr.indexOf(Math.max(...signupsArr))];
console.log(`\nTotal customers: ${total}`);
console.log(`Best cohort   : ${best}`);

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👥 Customer Signup Cohorts

1 · Monthly signups & cumulative growth

2 · Visualise cohort growth