In this applet the user can enter any number of points and any family of functions that contains up to four constants. The constants can be then changed dynamically at a press of an arrow. That allows for easy and quick matching a formula to given data points.
The first version of the applet gives the option of entering data points in several formats. Click the screen shot below to open the applet in a new window:
The second version of the applet displays other types of errors besides the least squares error. Click the screen shot below to open the second version of the applet in a new window:
Note: The complete source code for both applets is available in the article "Flash Tools for Developers: Matching Formulas to Data" that you can find at Custom Classes for Mathematics section of Flash and Math.