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CalcLogFit


Unit:SDL_math2
Class:TCurveFit
Declaration:procedure CalcLogFit (var k0, k1, FitQual: double);

The procedure CalcLogFit calculates the best fitting logarithmic curve for a given set of data. The curve is determined by the equation

y = k0 + k1 * ln(x)

The values of x and y are given by the data samples, the parameters k0 and k1 are estimated by CalcLogFit using a least squares approximation.

The data points [x,y] have to be entered using the routine EnterStatValue. A minimum number of 3 values is required in order to apply CalcLogFit. Do not forget to reset the statistics calculation before entering any new data sets (use the method Init)

In addition to the parameters k0 and k1 CalcLogFit the quality of fit FitQual. This parameter may vary between 0.0 and 1.0, indicating the best possible fit if FitQual equals 1.0.

Hint 1: The quality of fit calculated by CalcLogFit is not adjusted for the degree of freedoms in the regression parameters.

Hint 2: The x-values must not be zero. The curve fitting algorithm raises an exception in the case of zero values.

Example: CURVEFIT.DPR
  This application lets you draw points in a chart and calculate various types of regression curves. Note, that CURVEFIT.DPR uses the components RCHART and NUMLAB for the user interface, which are not included in the MATH2 package.

Example: This method is used in the following example program (see http://www.lohninger.com/examples.html for downloading the code): curvefit



Last Update: 2012-Oct-20