Two Dimensional Interpolate, Extrapolate, Cubic Spline, Polynomial Curve Fitting, Line Intersections, Minima, Maxima, First Derivative, Second Derivative, and other functions. Using it you may solve multivariate nonlinear regression problems. Xlfit adds a custom toolbar for polynomial and cubic spline data fitting and Savitsky - Golay and weighted data smoothing. The add-in functions can be invoked by selecting the appropriate button in the Xlfit toolbar or by inserting a user defined function into the worksheet.
Usage is detailed in the included help file.
If x is outside the range, it will extrapolate based on the last two points in the given data set. The Add-In produces three worksheet functions for linear, parabolic and cubic interpolation. The two dimensional lookup capability is especially useful for looking up swaption volatilities. There are many programs each with many options. Inc. All rights reserved.