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QuickStart Samples

One-Way Anova QuickStart Sample (Visual Basic)

Illustrates how to use the OneWayAnovaModel class to perform a one-way analysis of variance in Visual Basic.

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Option Infer On

Imports Extreme.DataAnalysis
Imports Extreme.Statistics

Namespace Extreme.Numerics.QuickStart.VB
    ' Illustrates the use of the OneWayAnovaModel class for performing 
    ' a one-way analysis of variance.
    Module AnovaOneWay

        Sub Main()
            ' This example investigates the effect of the color of packages
            ' on the sales of the product. The data comes from 12 stores.
            ' Packages can be either red, green or blue.

            ' Set up the data as anonymous records
            Dim data = {
                New With {.Store = 1, .Color = "Blue", .Shape = "Square", .Sales = 6},
                New With {.Store = 2, .Color = "Blue", .Shape = "Square", .Sales = 14},
                New With {.Store = 3, .Color = "Blue", .Shape = "Rectangle", .Sales = 19},
                New With {.Store = 4, .Color = "Blue", .Shape = "Rectangle", .Sales = 17},
                New With {.Store = 5, .Color = "Red", .Shape = "Square", .Sales = 18},
                New With {.Store = 6, .Color = "Red", .Shape = "Square", .Sales = 11},
                New With {.Store = 7, .Color = "Red", .Shape = "Rectangle", .Sales = 20},
                New With {.Store = 8, .Color = "Red", .Shape = "Rectangle", .Sales = 23},
                New With {.Store = 9, .Color = "Green", .Shape = "Square", .Sales = 7},
                New With {.Store = 10, .Color = "Green", .Shape = "Square", .Sales = 11},
                New With {.Store = 11, .Color = "Green", .Shape = "Rectangle", .Sales = 18},
                New With {.Store = 12, .Color = "Green", .Shape = "Rectangle", .Sales = 10}}
            Dim frame = DataFrame.FromObjects(data)

            ' Construct the OneWayAnovaModel object.
            Dim anova As New OneWayAnovaModel(frame, "Sales", "Color")
            ' Alternatively, you can use a formula to specify the variables
            anova = New OneWayAnovaModel(frame, "Sales ~ Color")

            ' Perform the calculation.
            anova.Compute()

            ' Verify that the design is balanced:
            If (Not anova.IsBalanced) Then
                Console.WriteLine("The design is not balanced.")
            End If

            ' The AnovaTable property gives us a classic anova table.
            ' We can write the table directly to the console:
            Console.WriteLine(anova.AnovaTable.ToString())
            Console.WriteLine()

            ' A Cell object represents the data in a cell of the model,
            ' i.e. the data related to one level of the factor.
            ' We can use it to access the group means of our color groups.

            ' First we get the IIndex object so we can easily iterate
            ' through the levels:
            Dim colorFactor = anova.GetFactor(Of String)(0)
            For Each level As String In colorFactor
                Console.WriteLine("Mean for group '{0}': {1:F4}",
                    level, anova.Cells.Get(level).Mean)
            Next

            ' We could have accessed the cells directly as well:
            Console.WriteLine("Variance for blue packages: {0}",
                anova.Cells.GetValue("Blue").Variance)
            Console.WriteLine()

            ' We can get the summary data for the entire model
            ' by using the TotalCell property:
            Dim totalSummary As Cell = anova.TotalCell
            Console.WriteLine("Summary data:")
            Console.WriteLine("# observations: {0}", totalSummary.Count)
            Console.WriteLine("Grand mean:     {0:F4}", totalSummary.Mean)

            Console.WriteLine("Press Enter key to continue.")
            Console.ReadLine()
        End Sub

    End Module

End Namespace