Update formatting and standard deviation calculation

CloudyDino · CloudyDino · commit c40ab47473e0 · 2018-03-12T14:53:20.000-04:00
Added periods to end of public comments and removed empty value tags as per iSazonov's request. Calculation of standard deviation is now cleaner.
diff --git a/src/Microsoft.PowerShell.Commands.Utility/commands/utility/Measure-Object.cs b/src/Microsoft.PowerShell.Commands.Utility/commands/utility/Measure-Object.cs
@@ -73,7 +73,7 @@ public GenericMeasureInfo()
         public double? Minimum { get; set; }
 
         /// <summary>
-        /// The Standard Deviation of property values
+        /// The Standard Deviation of property values.
         /// </summary>
         public double? StdDeviation { get; set; }
     }
@@ -135,7 +135,7 @@ public GenericObjectMeasureInfo()
         public object Minimum { get; set; }
 
         /// <summary>
-        /// The Standard Deviation of property values
+        /// The Standard Deviation of property values.
         /// </summary>
         public double? StdDeviation { get; set; }
     }
@@ -276,10 +276,9 @@ public MeasureObjectCommand()
         #endregion Common parameters in both sets
 
         /// <summary>
-        /// Set to true if Standard Deviation is to be returned
+        /// Set to true if Standard Deviation is to be returned.
         /// </summary>
-        /// <value></value>
-        [Parameter(ParameterSetName = GenericParameterSet)]
+            [Parameter(ParameterSetName = GenericParameterSet)]
         public SwitchParameter StdDeviation
         {
             get
@@ -746,9 +745,10 @@ private void AnalyzeNumber(double numValue, Statistics stat)
             }
             if (_measureStdDeviation && stat.count > 1)
             {
-                double countMinusOne = stat.count - 1;
-                double avgPrevious = stat.sumPrevious / countMinusOne;
-                stat.variance *= (countMinusOne - 1)/countMinusOne;
+                // Based off of iterative method of calculating variance on
+                // https://en.wikipedia.org/wiki/Algorithms_for_calculating_variance#Online_algorithm
+                double avgPrevious = stat.sumPrevious / (stat.count - 1);
+                stat.variance *= (stat.count - 2.0) / (stat.count - 1);
                 stat.variance += (numValue - avgPrevious) * (numValue - avgPrevious) / stat.count;
             }
         }

Original file line number	Diff line number	Diff line change
`@@ -73,7 +73,7 @@ public GenericMeasureInfo()`
`73`	`73`	`public double? Minimum { get; set; }`
`74`	`74`
`75`	`75`	`/// <summary>`
`76`		`- /// The Standard Deviation of property values`
	`76`	`+ /// The Standard Deviation of property values.`
`77`	`77`	`/// </summary>`
`78`	`78`	`public double? StdDeviation { get; set; }`
`79`	`79`	`}`
`@@ -135,7 +135,7 @@ public GenericObjectMeasureInfo()`
`135`	`135`	`public object Minimum { get; set; }`
`136`	`136`
`137`	`137`	`/// <summary>`
`138`		`- /// The Standard Deviation of property values`
	`138`	`+ /// The Standard Deviation of property values.`
`139`	`139`	`/// </summary>`
`140`	`140`	`public double? StdDeviation { get; set; }`
`141`	`141`	`}`
`@@ -276,10 +276,9 @@ public MeasureObjectCommand()`
`276`	`276`	`#endregion Common parameters in both sets`
`277`	`277`
`278`	`278`	`/// <summary>`
`279`		`- /// Set to true if Standard Deviation is to be returned`
	`279`	`+ /// Set to true if Standard Deviation is to be returned.`
`280`	`280`	`/// </summary>`
`281`		`- /// <value></value>`
`282`		`- [Parameter(ParameterSetName = GenericParameterSet)]`
	`281`	`+ [Parameter(ParameterSetName = GenericParameterSet)]`
`283`	`282`	`public SwitchParameter StdDeviation`
`284`	`283`	`{`
`285`	`284`	`get`
`@@ -746,9 +745,10 @@ private void AnalyzeNumber(double numValue, Statistics stat)`
`746`	`745`	`}`
`747`	`746`	`if (_measureStdDeviation && stat.count > 1)`
`748`	`747`	`{`
`749`		`- double countMinusOne = stat.count - 1;`
`750`		`- double avgPrevious = stat.sumPrevious / countMinusOne;`
`751`		`- stat.variance *= (countMinusOne - 1)/countMinusOne;`
	`748`	`+ // Based off of iterative method of calculating variance on`
	`749`	`+ // https://en.wikipedia.org/wiki/Algorithms_for_calculating_variance#Online_algorithm`
	`750`	`+ double avgPrevious = stat.sumPrevious / (stat.count - 1);`
	`751`	`+ stat.variance *= (stat.count - 2.0) / (stat.count - 1);`
`752`	`752`	`stat.variance += (numValue - avgPrevious) * (numValue - avgPrevious) / stat.count;`
`753`	`753`	`}`
`754`	`754`	`}`