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standardDeviation ​

Problem ​

You need the spread of a dataset — how far values typically deviate from the mean.

Solution ​

Use standardDeviation(array, callback?) to compute the population standard deviation.

ts
import { standardDeviation } from '@vielzeug/arsenal';

standardDeviation([2, 4, 4, 4, 5, 5, 7, 9]); // 2

const data = [{ value: 10 }, { value: 20 }, { value: 30 }];
standardDeviation(data, (d) => d.value); // ~8.165

Pitfalls ​

  • Computes population standard deviation (divide by N), not sample standard deviation (divide by N−1).
  • Returns NaN for empty arrays.