1234567891011121314151617181920212223242526272829303132333435363738394041424344454647484950515253545556575859
/** * The [Geometric Mean](https://en.wikipedia.org/wiki/Geometric_mean) is * a mean function that is more useful for numbers in different * ranges. * * This is the nth root of the input numbers multiplied by each other. * * The geometric mean is often useful for * **[proportional growth](https://en.wikipedia.org/wiki/Geometric_mean#Proportional_growth)**: given * growth rates for multiple years, like _80%, 16.66% and 42.85%_, a simple * mean will incorrectly estimate an average growth rate, whereas a geometric * mean will correctly estimate a growth rate that, over those years, * will yield the same end value. * * This runs in `O(n)`, linear time, with respect to the length of the array. * * @param {Array<number>} x sample of one or more data points * @returns {number} geometric mean * @throws {Error} if x is empty * @throws {Error} if x contains a negative number * @example * var growthRates = [1.80, 1.166666, 1.428571]; * var averageGrowth = ss.geometricMean(growthRates); * var averageGrowthRates = [averageGrowth, averageGrowth, averageGrowth]; * var startingValue = 10; * var startingValueMean = 10; * growthRates.forEach(function(rate) { *   startingValue *= rate; * }); * averageGrowthRates.forEach(function(rate) { *   startingValueMean *= rate; * }); * startingValueMean === startingValue; */function geometricMean(x) {    if (x.length === 0) {        throw new Error("geometricMean requires at least one data point");    }
    // the starting value.    let value = 1;
    for (let i = 0; i < x.length; i++) {        // the geometric mean is only valid for positive numbers        if (x[i] < 0) {            throw new Error(                "geometricMean requires only non-negative numbers as input"            );        }
        // repeatedly multiply the value by each number        value *= x[i];    }
    return Math.pow(value, 1 / x.length);}
export default geometricMean;