IDmMethodCrossValidation.NumberOfFolds

Syntax

NumberOfFolds: Integer;

Description

The NumberOfFolds property determines the number of folds.

Comments

The property is taken into account if the K-fold cross-validation is used, that is, the IDmMethodCrossValidation.SamplingType property is set to CrossValidationSamplingType.Kfold.

Range of available values: [1; number of observations].

The default value: 5.

Example

Executing the example requires that the repository contains a table with the DM_TABLE identifier containing data for analysis.

Add links to the Metabase, Ms, Stat system assemblies.

Sub UserProc;
Var
    MB: IMetabase;
    ReportDS: IDmReportDataSource;
    TableDS: IDmTableDataSource;
    Method: IDmMethod;
    DM: IDmLogisticRegression;
    i, j: Integer;
    Attrs: Array Of Integer;
    CrossValidation: IDmMethodCrossValidation;
    Reports: IDmReports;
    DmReport: IDmReport;
    CrossValPerf: ICrossValidationPerformanceScores;
    CategoriesList, KfoldIntervals: Array Of Integer;
    PerformanceMatrix: Array Of Double;
Begin
    MB := MetabaseClass.Active;
    // Create calculation method
    Method := (New DataMiningMethod.Create) As IDmMethod;
    // Specify method type
    Method.Kind := DmMethodKind.LogisticRegression;
    // Create table data source
    TableDS := (New TableDataSource.Create) As IDmTableDataSource;
    // Determine source table
    TableDS.Table := MB.ItemByID("DM_TABLE").Bind;
    // Set input data source
    Method.InputDataSource := TableDS;
    // Create a data source that is a regular report
    ReportDS := (New ReportDataSource.Create) As IDmReportDataSource;
    // Set data consumer
    Method.OutputDataSource := ReportDS;
    // Set up calculation method parameters
    DM := Method.Details As IDmLogisticRegression;
    // Set factors impacting analyzed attribute
    Attrs := New Integer[TableDS.FieldCount - 1];
    For i := 0 To Attrs.Length - 1 Do
        Attrs[i] := i + 1;
    End For;
    DM.Attributes := Attrs;
    // Specify analyzed object
    DM.Target := ReportDS.FieldCount;
    // Set threshold
    DM.Threshold := 0.57;
    // Set up cross-validation parameters
    CrossValidation := DM.CrossValidation;
    // Specify that cross-validation is used
    CrossValidation.Active := True;
    // Set cross-validation method:  K -fold cross-validation
    CrossValidation.SamplingType := CrossValidationSamplingType.Kfold;
    // Set number of folds
    CrossValidation.NumberOfFolds := 4;
    // Perform analysis and output results
    Reports := Method.Execute;
    // Display cross-validation results
    DmReport := Reports.FindByType(DmReportType.CrossValidation);
    DmReport.Generate;
    CrossValPerf := CrossValidation.Results;
    Debug.WriteLine("Cross-validation results:");
    Debug.Indent;
    Debug.WriteLine("Analyzed attribute: " + CrossValPerf.ClassificatorName);
    Debug.Write("Number of factors influencing the analyzed attribute: ");
    Debug.WriteLine(CrossValPerf.FactorsNumber);
    Debug.WriteLine("Number of observations: " + CrossValPerf.ObservationsNumber.ToString);
    Debug.WriteLine("Number of repetitions: " + CrossValidation.NumberOfRandomTests.ToString);
    Debug.WriteLine("Accuracy of classification: " + CrossValPerf.ClassificationAccuracy.ToString);
    Debug.WriteLine("Categories:");
    Debug.Indent;
    CategoriesList := CrossValPerf.CategoriesList;
    For i := 0 To CategoriesList.Length - 1 Do
        Debug.WriteLine(CategoriesList[i]);
    End For;
    Debug.Unindent;
    Debug.WriteLine("Fold intervals:");
    Debug.Indent;
    KfoldIntervals := CrossValPerf.KfoldIntervals;
    For i := 0 To KfoldIntervals.Length - 1 Do
        Debug.WriteLine(KfoldIntervals[i]);
    End For;
    Debug.Unindent;
    Debug.WriteLine("Correct classification:");
    Debug.Indent;
    PerformanceMatrix := CrossValPerf.PerformanceMatrix;
    For i := 0 To PerformanceMatrix.GetUpperBound(1) Do
        For j := 0 To PerformanceMatrix.GetUpperBound(2) Do
            Debug.Write(PerformanceMatrix[i, j].ToString + #9);
        End For;
    Debug.WriteLine("");
    End For;
    Debug.Unindent;
    Debug.Unindent;
End Sub UserProc;

After executing the example cross-validation is executed, its results are displayed in the console window.