| 1 | import { isEmptyArray, isNullOrUndefined } from './Utils'; |
| 2 | |
| 3 | export const median = (dataSet: number[]): number => { |
| 4 | if (isEmptyArray(dataSet)) { |
| 5 | return 0; |
| 6 | } |
| 7 | if (Array.isArray(dataSet) === true && dataSet.length === 1) { |
| 8 | return dataSet[0]; |
| 9 | } |
| 10 | const sortedDataSet = dataSet.slice().sort((a, b) => a - b); |
| 11 | return ( |
| 12 | (sortedDataSet[(sortedDataSet.length - 1) >> 1] + sortedDataSet[sortedDataSet.length >> 1]) / 2 |
| 13 | ); |
| 14 | }; |
| 15 | |
| 16 | // TODO: use order statistics tree https://en.wikipedia.org/wiki/Order_statistic_tree |
| 17 | export const nthPercentile = (dataSet: number[], percentile: number): number => { |
| 18 | if (percentile < 0 && percentile > 100) { |
| 19 | throw new RangeError('Percentile is not between 0 and 100'); |
| 20 | } |
| 21 | if (isEmptyArray(dataSet)) { |
| 22 | return 0; |
| 23 | } |
| 24 | const sortedDataSet = dataSet.slice().sort((a, b) => a - b); |
| 25 | if (percentile === 0 || sortedDataSet.length === 1) { |
| 26 | return sortedDataSet[0]; |
| 27 | } |
| 28 | if (percentile === 100) { |
| 29 | return sortedDataSet[sortedDataSet.length - 1]; |
| 30 | } |
| 31 | const percentileIndexBase = (percentile / 100) * (sortedDataSet.length - 1); |
| 32 | const percentileIndexInteger = Math.floor(percentileIndexBase); |
| 33 | if (!isNullOrUndefined(sortedDataSet[percentileIndexInteger + 1])) { |
| 34 | return ( |
| 35 | sortedDataSet[percentileIndexInteger] + |
| 36 | (percentileIndexBase - percentileIndexInteger) * |
| 37 | (sortedDataSet[percentileIndexInteger + 1] - sortedDataSet[percentileIndexInteger]) |
| 38 | ); |
| 39 | } |
| 40 | return sortedDataSet[percentileIndexInteger]; |
| 41 | }; |
| 42 | |
| 43 | export const stdDeviation = (dataSet: number[]): number => { |
| 44 | let totalDataSet = 0; |
| 45 | for (const data of dataSet) { |
| 46 | totalDataSet += data; |
| 47 | } |
| 48 | const dataSetMean = totalDataSet / dataSet.length; |
| 49 | let totalGeometricDeviation = 0; |
| 50 | for (const data of dataSet) { |
| 51 | const deviation = data - dataSetMean; |
| 52 | totalGeometricDeviation += deviation * deviation; |
| 53 | } |
| 54 | return Math.sqrt(totalGeometricDeviation / dataSet.length); |
| 55 | }; |