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   Curve Fitting Software

    CurveFit/X 5.0
Curve Fitting ActiveX Control and COM Object

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Curve Fit/X ActiveX Control implements curve fitting functions including smooth cubic splines and polynomial regression models.

Features of Curve Fit/X

Curve Fit/X is both an ActiveX Control and a COM object, implemented in a single DLL, yet it can be used in a wide range of programming languages that support these standards. This includes Visual Basic 6, Visual Basic .NET, Visual C++, Visual C#, Excel - VBA, Delphi and Borland C++ Builder.

One of the most well known and respected methods that can be used to fit smooth curves through multiple data points is the Smoothed Cubic Spline, developed originally by Reinsch in 1967. This method enables the usual cubic spline model to be extended to the case where, instead of fitting a spline model through all data points (knots), which could result in a very "wriggly" curve, allows a smooth curve to be fit to the data. Unlike polynomial models however, which can perform poorly on some data sets, since each data point can affect the polynomial over the whole range of the data, the smoothed cubic spline model retains the flexible approximation capabilities of regular spline models coupled with the smoothing characteristics of the Reinsch algorithm.

This method fits a Smooth Cubic Spline to the input data. A weight matrix C is returned, which can then be used in the corresponding cubic spline method. The polynomial is of the form:

f(x) = ai + bihi + cihi2 + dihi3

where h x - xi,    xi <= x < xi+1  i=0, 1,..., n-1.


Source Code Examples

Curve Fit/X includes sample applications - with full source code, in the following programming languages:        

          Visual C#
          Visual Basic .NET
          Visual Basic 6

The control can also be used to create curve fitting software within other programming languages such as Delphi, Visual C++ .NET, Visual C++ 6 (Windows and Console applications), Borland C++ Builder, Excel an Access. Contact us if you need assistance in creating your application using this component or any others we provide.

Curve Fit/X ActiveX Control

The control is written as a lightweight ATL C/C++ object, and does not require bulky MFC DLLs. Because the control is written in ATL it is efficient and small in size. The numerical processing is written in C for speed, and integrated into the lightweight ATL/C++ framework. Using our controls is very easy! Enjoy the speed and robustness of industrial-strength C/C++ in your application, with only a single line of code.

If you can use any of the existing components in Visual Basic or whatever language environment you program in, then you will have absolutely no problem in using Windale Technologies components and controls.

Trial Version

Curve Fit/X Trial Version is limited to processing up to 100 data points, however all functions are available. Develop and test curve fitting applications on your data or use known benchmark data sets such as the Titanium Heat Data.

Curve fitting sample program created using Curve Fit/X. 
Other sample applications with full source code are also included.

If you do have any questions or concerns about using our controls - all you need to do is email us and we will assist you in learning how to use our controls. Just take a look at our testimonials page to see some of the comments we have received from happy customers. we receive many emails from people who have questions about our products or who need a little assistance to get started using an ActiveX control in their program - don't hesitate to contact us and we will be pleased to help you.

Do you require some function that we don't already have? Contact us and we may be able to extend our controls to do what you require.

Curve Fit/X ActiveX and COM Control

Curve Fit/X is an ActiveX DLL that can be used in wide range of Windows applications. It requires no user interface and can be accessed by any ActiveX compatible development environment, including VB, ASP, VBA, VC++, VC#, Borland C++ Builder and Delphi.

Curve Fit/X supports threaded blocking and non-blocking modes. This means for lengthy computations, you can use the control in a program, pass it some data for processing and the program can then run other tasks and respond to user input while the computations are taking place. When processing is complete, an event is fired and the program continues from the data processing step. This blocking/non-blocking mode is under program control. Error codes are returned from the event indicating the success or otherwise of the data processing. The computations can also be interrupted under program control by the user, for example, it is straight forward to implement a "Stop" button to direct the computations to be stopped.

Matrix data used with Curve Fit/X and returned from the control can have different index starting values. This means that you can choose to index your data from 0 or 1. Curve Fit/X will pass the data back in an array indexed from the value you specify in a property of the control. All data used and returned with Curve Fit/X is in double format. This means it is suitable for use with Visual Basic and Visual C++. Moreover, the data is in a format compatible with further numeric processing. Hence, if you wish to use the data with other controls that can use double format arrays, this presents no problems.


  1. Reinsch, C. H., "Smoothing by Spline Functions",  Numerische Mathematik 10, 177-183, 1967.