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x/simplestatistics/src/variance.js

simple statistics for node & browser javascript
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import sumNthPowerDeviations from "./sum_nth_power_deviations.js";
/** * The [variance](http://en.wikipedia.org/wiki/Variance) * is the sum of squared deviations from the mean. * * This is an implementation of variance, not sample variance: * see the `sampleVariance` method if you want a sample measure. * * @param {Array<number>} x a population of one or more data points * @returns {number} variance: a value greater than or equal to zero. * zero indicates that all values are identical. * @throws {Error} if x's length is 0 * @example * variance([1, 2, 3, 4, 5, 6]); // => 2.9166666666666665 */function variance(x) { if (x.length === 0) { throw new Error("variance requires at least one data point"); }
// Find the mean of squared deviations between the // mean value and each value. return sumNthPowerDeviations(x, 2) / x.length;}
export default variance;