IModelling.Ln

Syntax

Ln(Input: Variant): Variant;

Parameters

Input. Variable.

Description

The Ln method returns a natural logarithm of specified variable points.

Comments

The point value, for which the logarithm is found, and its base must be greater than zero.

Example

Executing the example requires that the repository contains a modeling container with the MS identifier. This container includes a model with the MODEL_D identifier that is calculated by the determinate equation method and contains at least one input variable.

Add links to the Metabase and Ms system assemblies.

Sub UserProc;
Var
    Mb: IMetabase;
    ModelSpace, ModelObj: IMetabaseObject;
    Transf: IMsFormulaTransform;
    Formula: IMsFormula;
    Model: IMsModel;
    Determ: IMsDeterministicTransform;
    TransVar: IMsFormulaTransformVariable;
    Slice: IMsFormulaTransformSlice;
    TermInfo: IMsFormulaTermInfo;
    Expr: IExpression;
Begin
    // Get repository
    Mb := MetabaseClass.Active;
    // Get modeling container
    ModelSpace := Mb.ItemById("MS").Bind;
    // Get model
    ModelObj := Mb.ItemByIdNamespace("MODEL_D", ModelSpace.Key).Edit;
    Model := ModelObj As IMsModel;
    // Get model calculation parameters
    Transf := Model.Transform;
    Formula := Transf.FormulaItem(0);
    Determ := Formula.Method As IMsDeterministicTransform;
    // Get the first input variable
    TransVar := Transf.Inputs.Item(0);
    Slice := TransVar.Slices.Item(0);
    TermInfo := Transf.CreateTermInfo;
    TermInfo.Slice := Slice;
    // Set mode of passing variable into calculation
    TermInfo.Type := MsFormulaTermType.Pointwise;
    // Get model calculation expression
    Expr := Determ.Expression;
    Expr.References := "Ms";
    // Set model calculation expression
    Expr.AsString := "Ln(" + TermInfo.TermInnerText + ")";
    // Check if the expression is correct
    If Expr.Valid
        // If the expression is set correctly, save the model
        Then ModelObj.Save;
        // If expression is not correct, output message to console window
        Else Debug.WriteLine("Model is not saved: error in the formula");
    End If;
End Sub UserProc;

After executing the example the model will calculate natural logarithm of the first input variable points.

Example of Use in Expressions

Expression 1:

Ln({Brazil|BCA})

Result: natural logarithm of Brazil|BCA factor observations is calculated.

Use: it can be used in formulas of cross functional expression editor in any platform tool where it is available.

Expression 2:

Ln(X1)

Result: natural logarithm is calculated for the X1 factor points.

Use: it can be used in model formulas of modeling container based on variables.

Expression 3:

Ln(4)

Result: 1.39.

Application: it can be used in any expressions.