FitUtil

Overview

FitUtil is a Dyalog Unicode Workspace (v14.1) that contains useful functions related to curve fitting using the domino operator (⌹). The results are shown in plain text in the session and graphically using WPF. The regressions performed are:

 1. Linear:      Y' = a + b×X
 2. Exponential: Y' = a × exp(b×X)
 3. Power:       Y' = a × X*b
 4. Logarithmic: Y' = a + b×ln(X)
 5. Parabolic:   Y' = a + b×X + c×X*2
 6. Cubic:       Y' = a + b×X + c×X*2 + d×X*3
 7. Linear through origin:    Y' = 0 + b×X
 8. Parabolic through origin: Y' = 0 + b×X + c×X*2
 9. Cubic through origin:     Y' = 0 + b×X + c×X*2 + d×X*3
10. Weibull:                  Y' = a × exp(b×X*c)

The first 9 curve fittings are a least square fit using the APL's domino operator. The Weibull regression is obtained by iterations and may not converge to a solution all the time.
The main functions are FIT and TFIT. Both will perform 10 different curve fittings on a set of X and Y values.

The function TFIT will removed the non-significatives points by performing a Student test on the data.

The results are stored in a global nested variable called ∆FIT or ∆TFIT depending of the main function used.

FIT and TFIT will present the results of the curve fittings in the APL session, the function SHOW will present them graphically using ∆FIT or ∆TFIT. It uses WPF and the Syncfusion libraries.

The usage of the functions is as follow:

x FIT y
SHOW ∆FIT

x TFIT y
SHOW ∆TFIT