Computer Programming/Min-Max Normalisation

From Wikibooks, open books for an open world
Jump to navigation Jump to search

SQL[edit]

SET ANSI_NULLS ON
GO
SET QUOTED_IDENTIFIER ON
GO

-- =============================================
-- Author:	Colm Rice
-- Description:	Gets min-max normalised value of a variable
-- Bog standard version (based upon a linear eqn of the form: Ax+B)
-- Transforms a value into the range [0,1]
-- Bulletproof checks: 
--	NB: If division by zero returning -1.0 to alert the user!
--	Any nulls going down are replaced with zero
-- =============================================

ALTER FUNCTION dbo.GetMinMaxNorm
(
	@valueToBeNormalised decimal(10,2),
	@maxValue decimal(10,2),
	@minValue decimal(10,2)
)
RETURNS decimal(10,2)
AS
BEGIN
	DECLARE @range decimal(10,2)
	DECLARE @result decimal(10,2)

	SET @range = ISNULL(@maxValue, 0.0) - ISNULL(@minValue, 0.0)
	
	if(@range = 0)	--Bulletproof
		return -1.0
	else
		SET @result = (ISNULL(@valueToBeNormalised, 0) - ISNULL(@minValue, 0)) / @range

	return @result

END
GO

VB.Net[edit]

    ''' <summary>
    ''' Gets the min-max normalised value of a variable
    ''' Bog standard version (based upon a linear eqn)
    ''' </summary>
    ''' <param name="value">Value to be tranformed</param>
    ''' <param name="maxValue">Max value of variable set</param>
    ''' <param name="minValue">Min value of variable set</param>
    ''' <returns>Normalised value in the range [0,1]</returns>
    ''' <remarks>Division by zero check. Returns NaN to alert user!</remarks>
    Public Function GetMinMaxNorm(ByVal value As Double, ByVal maxValue As Double, ByVal minValue As Double) As Double

        Dim range As Double
        range = maxValue - minValue

        If (range = 0) Then 'Bulletproof
            Return Double.NaN
        Else
            Return ((value - minValue) / range)
        End If

    End Function


C#[edit]

        /// <summary>
        /// Gets the min-max normalised value of a variable
        /// Bog standard version (based up on a linear eqn)
        /// NB: Division by zero return NaN to alert user
        /// </summary>
        /// <param name="value">Value to be transformed</param>
        /// <param name="minValue">Min value over the variable set</param>
        /// <param name="maxValue">Max value of the variable set</param>
        /// <returns>Value in the range [0,1]</returns>
        public double GetMinMaxNorm(double value, double maxValue, double minValue)
        {
            double range = maxValue - minValue;

            if (range == 0)     //Bulletproofing
                return double.NaN;
            else
                return (value - minValue) / range;
        }