ISmLinearRegress.GDLTerms

Syntax

Description

The GDLTerms property determines parameters for estimation of Koyck distributed lags.

Comments

The ISmLinearRegress.UseGDLTerms property determines whether to use Koyck distributed lags model.

Example

To execute the example, add a link to the Stat system assembly.

Sub UserProc;
Var
    lr: ISmLinearRegress;
    y, x1, x3: Array[25] Of Double;
    i: Integer;
    init: Array[2] Of Double;
    constant: IIntercept;
    exp: ISlSeries;
    GDLTerms: ISlGDLTerms;
    coefs: ICoefficients;
Begin

    // Set variable values
    Y[0] := -0.22;  X1[0]:=0.37; X3[0]:=-135;
    Y[1] := -0.3;   X1[1]:=0.19; X3[1]:=-135;
    Y[2] := -0.34;  X1[2]:=0.08; X3[2]:=-133;
    Y[3] := -0.34;  X1[3]:=0.08; X3[3]:=-129;
    Y[4] := -0.34;  X1[4]:=0.13; X3[4]:=-125;
    Y[5] := -0.34;  X1[5]:=0.21; X3[5]:=-123;
    Y[6] := -0.3;   X1[6]:=0.37; X3[6]:=-121;
    Y[7] := -0.28;  X1[7]:=0.43; X3[7]:=-117;
    Y[8] := -0.22; X1[8]:=0.49; X3[8]:=-115;
    Y[9] := -0.11; X1[9]:=0.55; X3[9]:=-112;
    Y[10] := -0.04; X1[10]:=0.65;   X3[10]:=-109;
    Y[11] := -0.01; X1[11]:=0.73; X3[11]:=-106;
    Y[12] := 0.06; X1[12] := 0.98; X3[12]:=-109;
    Y[13] := 0.09; X1[13] := 1.1;   X3[13]:=-109;
    Y[14] := 0.17; X1[14] := 1.19;  X3[14]:=-115;
    Y[15] := 0.31; X1[15] := 1.26;  X3[15]:=-117;
    Y[16] := 0.37; X1[16] := 1.43;  X3[16]:=-123;
    Y[17] := 0.46; X1[17] := 1.62;  X3[17]:=-123;
    Y[18] := 0.57; X1[18] := 1.72;  X3[18]:=-125;
    Y[19] := 0.62; X1[19] := 1.77;  X3[19]:=-129;
    Y[20] := 0.62; X1[20] := 1.77;  X3[20]:=-133;
    Y[21] := 0.62; X1[21] := 1.77;  X3[21]:=-135;
    Y[22] := 0.62; X1[22] := 1.77;  X3[22]:=-135;
    Y[23] := 0.54; X1[23] := 1.72; X3[23]:=-135;
    Y[24] := 0.58; X1[24] := 1.48;  X3[24]:=-129;

    // Create a method
    lr := New SmLinearRegress.Create;
    // Determine parameters of sample periods and forecasting
    lr.ModelPeriod.FirstPoint := 0;
    lr.ModelPeriod.LastPoint := 15;
    lr.Forecast.LastPoint := 25;
    // Determine constant parameters
    constant := lr.ModelCoefficients.Intercept;
    constant.Mode := InterceptMode.AutoEstimate;
    // Set explained variable
    lr.Explained.Value := y;
    // Set explanatory variables
    exp := lr.Explanatories;
    exp.Add.Value := x1;
    exp.Add.Value := x3;
    // Set Koyck lag parameters
    lr.UseGDLTerms := True;
    GDLTerms := lr.GDLTerms;
    // Determine maximum number of iterations
    GDLTerms.MaxIteration := 300;
    // Determine accuracy used in optimization
    GDLTerms.Tolerance := 0.01;
    // Use numeric derivatives
    GDLTerms.UseAnalyticDeriv := False;
    // Set initial coefficient values
    init[0] := 0.011;
    init[1] := 0.024;
    GDLTerms.AllInitialValues := init;
    // Execute method calculation
    i := lr.Execute;

    // Display results
    If i = 0 Then
        Debug.WriteLine("Constant value: " + constant.Estimate.ToString);
        Debug.WriteLine("Modeling series:");
        Debug.Indent;
        For i := 0 To lr.Fitted.Length - 1 Do
            Debug.WriteLine(lr.Fitted[i]);
        End For;
        Debug.Unindent;
        Debug.WriteLine("Forecasting series:");
        Debug.Indent;
        For i := 0 To lr.Forecast.Value.Length - 1 Do
            Debug.WriteLine(lr.Forecast.Value[i]);
        End For;
        Debug.Unindent;
        coefs := lr.ModelCoefficients.Coefficients;
        Debug.WriteLine("Coefficient values:");
        Debug.Indent;
        Debug.WriteLine("beta0_1: " + coefs.Estimate[0].ToString);
        Debug.WriteLine("beta0_2: " + coefs.Estimate[1].ToString);
        Debug.WriteLine("alpha: " + coefs.Estimate[2].ToString);
        Debug.Unindent;
    End If;
End Sub UserProc;

After executing the example the console window displays results of linear regression model calculation (OLS estimation) using Koyck distributed lags: modeling explained series, forecasting series, and coefficient values.