hes@ecsvax.UUCP (06/27/84)
<>Three points in a plane define a conic section. However there are many types of conic sections. While a circle is a conic section which can be defined by three points - what if they are colinear? Then the circle has an infinite radius - and certainly is hard to recognize as a circle. It sure looks like a straight line, which also is a conic section. I agree with the many comments which have suggested that first one must define the family of curves acceptable, and then start fitting. Fitting methodologies include statistical ones such as Least Squares and Maximum Likelihood which generally don't pass through all the data points, as well as the splines which were discussed in an earlier note. (I prefer that the family be chosen from a knowledge of the origin of the data, i.e., a realistic model.) --henry schaffer genetics ncsu