From aeada1fa7a7ab2d443cb1af7585a4ec506bad6bd Mon Sep 17 00:00:00 2001
From: =?utf8?q?J=C3=A9r=C3=B4me=20Benoit?= <jerome.benoit@sap.com>
Date: Sun, 2 May 2021 18:26:09 +0200
Subject: [PATCH] Add standard deviation computation to time statistics
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Signed-off-by: Jérôme Benoit <jerome.benoit@sap.com>
---
 src/types/CommandStatistics.ts |  1 +
 src/utils/Statistics.ts        | 15 +++++++++++++++
 2 files changed, 16 insertions(+)

diff --git a/src/types/CommandStatistics.ts b/src/types/CommandStatistics.ts
index 84f2bdca..e4804f8a 100644
--- a/src/types/CommandStatistics.ts
+++ b/src/types/CommandStatistics.ts
@@ -20,6 +20,7 @@ export interface CommandStatisticsData {
   totalTimeMeasurement: number;
   avgTimeMeasurement: number;
   medTimeMeasurement: number;
+  stdDevTimeMeasurement: number;
 }
 
 export default interface CommandStatistics {
diff --git a/src/utils/Statistics.ts b/src/utils/Statistics.ts
index d194451a..65e3be5b 100644
--- a/src/utils/Statistics.ts
+++ b/src/utils/Statistics.ts
@@ -96,6 +96,20 @@ export default class Statistics {
     return (sortedDataSet[(middleIndex - 1)] + sortedDataSet[middleIndex]) / 2;
   }
 
+  private 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);
+  }
+
   private addPerformanceTimer(command: RequestCommand | IncomingRequestCommand, duration: number): void {
     // Map to proper command name
     const MAPCOMMAND = {
@@ -119,6 +133,7 @@ export default class Statistics {
     this.commandsStatistics.commandsStatisticsData[command].avgTimeMeasurement = this.commandsStatistics.commandsStatisticsData[command].totalTimeMeasurement / this.commandsStatistics.commandsStatisticsData[command].countTimeMeasurement;
     Array.isArray(this.commandsStatistics.commandsStatisticsData[command].timeMeasurementSeries) ? this.commandsStatistics.commandsStatisticsData[command].timeMeasurementSeries.push(duration) : this.commandsStatistics.commandsStatisticsData[command].timeMeasurementSeries = [duration] as CircularArray<number>;
     this.commandsStatistics.commandsStatisticsData[command].medTimeMeasurement = this.median(this.commandsStatistics.commandsStatisticsData[command].timeMeasurementSeries);
+    this.commandsStatistics.commandsStatisticsData[command].stdDevTimeMeasurement = this.stdDeviation(this.commandsStatistics.commandsStatisticsData[command].timeMeasurementSeries);
   }
 
   private logPrefix(): string {
-- 
2.34.1