65 lines
2.0 KiB
JavaScript
65 lines
2.0 KiB
JavaScript
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// Helpers
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const sum = (array) => array.reduce((a, b) => a + b, 0);
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const probabilityToOdds = (p) => p / (1 - p);
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const oddsToProbability = (o) => o / (1 + o);
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// Main functions
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export const median = (array) => {
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// needs validation array not empty
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let midway = Math.floor(array.length);
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let arrayToBeSorted = [...array];
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// sorting mutates the array, which I am averse to
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let arraySorted = arrayToBeSorted.sort((a, b) => a - b);
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if (midway % 2) {
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return arraySorted[midway];
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} else {
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return (arraySorted[midway - 1] + arraySorted[midway]) / 2;
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}
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};
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export const arithmeticMean = (array) => {
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let result = sum(array) / array.length;
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return result;
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};
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export const geometricMean = (array) => {
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// sum of logs seems more numerically stable than multiplying a lot of numbers 0<=p<=1
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let arrayAsLog = array.map((p) => Math.log(p));
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let sumOfLogs = sum(arrayAsLog) / arrayAsLog.length;
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let result = Math.exp(sumOfLogs);
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return result;
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};
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export const geometricMeanOfOdds = (array) => {
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let arrayOfOdds = array.map((p) => probabilityToOdds(p));
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let arrayOfLogsOfOdds = arrayOfOdds.map((p) => Math.log(p));
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let sumOfLogsOfOdds = sum(arrayOfLogsOfOdds) / arrayOfLogsOfOdds.length;
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let geomMeanOfOdds = Math.exp(sumOfLogsOfOdds);
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let result = oddsToProbability(geomMeanOfOdds);
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return result;
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};
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export const extremizedGeometricMeanOfOdds = (
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array,
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extremizationParameter = 1.5
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) => {
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let arrayOfOdds = array.map((p) => probabilityToOdds(p));
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let arrayOfLogsOfOdds = arrayOfOdds.map((p) => Math.log(p));
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let extremizedSumOfLogsOfOdds =
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(extremizationParameter * sum(arrayOfLogsOfOdds)) /
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arrayOfLogsOfOdds.length;
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let extremizedGeomMeanOfOdds = Math.exp(extremizedSumOfLogsOfOdds);
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let result = oddsToProbability(extremizedGeomMeanOfOdds);
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return result;
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};
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export const neyman = (array) => {
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let n = array.length;
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let d =
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(n * (Math.sqrt(3 * Math.pow(n, 2) - 3 * n + 1) - 2)) /
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(Math.pow(n, 2) - n - 1);
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let result = extremizedGeometricMeanOfOdds(array, d);
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return result;
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};
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