X-Git-Url: https://git.piment-noir.org/?a=blobdiff_plain;f=src%2Futils%2FStatisticUtils.ts;h=2ff71b0acb2ffa897a5d07f0e7bcd18719314903;hb=de7b9e0583275225509c099f75a2801371da54d0;hp=bb9a847091decf2ca488f83ad8c3d9d579d6e7fd;hpb=4884b8d37eebb90a39a8295f1b61cf822dcf0869;p=e-mobility-charging-stations-simulator.git

diff --git a/src/utils/StatisticUtils.ts b/src/utils/StatisticUtils.ts
index bb9a8470..2ff71b0a 100644
--- a/src/utils/StatisticUtils.ts
+++ b/src/utils/StatisticUtils.ts
@@ -1,7 +1,31 @@
-import { Utils } from './Utils';
+import { isEmptyArray, isNullOrUndefined } from './Utils';
 
+/**
+ * Computes the average of the given data set.
+ *
+ * @param dataSet - Data set.
+ * @returns The average of the given data set.
+ * @internal
+ */
+export const average = (dataSet: number[]): number => {
+  if (Array.isArray(dataSet) && dataSet.length === 0) {
+    return 0;
+  }
+  if (Array.isArray(dataSet) && dataSet.length === 1) {
+    return dataSet[0];
+  }
+  return dataSet.reduce((accumulator, nb) => accumulator + nb, 0) / dataSet.length;
+};
+
+/**
+ * Computes the median of the given data set.
+ *
+ * @param dataSet - Data set.
+ * @returns The median of the given data set.
+ * @internal
+ */
 export const median = (dataSet: number[]): number => {
-  if (Utils.isEmptyArray(dataSet)) {
+  if (isEmptyArray(dataSet)) {
     return 0;
   }
   if (Array.isArray(dataSet) === true && dataSet.length === 1) {
@@ -18,7 +42,7 @@ export const nthPercentile = (dataSet: number[], percentile: number): number =>
   if (percentile < 0 && percentile > 100) {
     throw new RangeError('Percentile is not between 0 and 100');
   }
-  if (Utils.isEmptyArray(dataSet)) {
+  if (isEmptyArray(dataSet)) {
     return 0;
   }
   const sortedDataSet = dataSet.slice().sort((a, b) => a - b);
@@ -30,7 +54,7 @@ export const nthPercentile = (dataSet: number[], percentile: number): number =>
   }
   const percentileIndexBase = (percentile / 100) * (sortedDataSet.length - 1);
   const percentileIndexInteger = Math.floor(percentileIndexBase);
-  if (!Utils.isNullOrUndefined(sortedDataSet[percentileIndexInteger + 1])) {
+  if (!isNullOrUndefined(sortedDataSet[percentileIndexInteger + 1])) {
     return (
       sortedDataSet[percentileIndexInteger] +
       (percentileIndexBase - percentileIndexInteger) *
@@ -40,16 +64,27 @@ export const nthPercentile = (dataSet: number[], percentile: number): number =>
   return sortedDataSet[percentileIndexInteger];
 };
 
-export const stdDeviation = (dataSet: number[]): number => {
-  let totalDataSet = 0;
-  for (const data of dataSet) {
-    totalDataSet += data;
-  }
-  const dataSetMean = totalDataSet / dataSet.length;
-  let totalGeometricDeviation = 0;
-  for (const data of dataSet) {
-    const deviation = data - dataSetMean;
-    totalGeometricDeviation += deviation * deviation;
-  }
-  return Math.sqrt(totalGeometricDeviation / dataSet.length);
+/**
+ * Computes the sample standard deviation of the given data set.
+ *
+ * @param dataSet - Data set.
+ * @param dataSetAverage - Average of the data set.
+ * @returns The sample standard deviation of the given data set.
+ * @see https://en.wikipedia.org/wiki/Unbiased_estimation_of_standard_deviation
+ * @internal
+ */
+export const stdDeviation = (
+  dataSet: number[],
+  dataSetAverage: number = average(dataSet),
+): number => {
+  if (isEmptyArray(dataSet)) {
+    return 0;
+  }
+  if (Array.isArray(dataSet) && dataSet.length === 1) {
+    return 0;
+  }
+  return Math.sqrt(
+    dataSet.reduce((accumulator, num) => accumulator + Math.pow(num - dataSetAverage, 2), 0) /
+      (dataSet.length - 1),
+  );
 };