Curve Fitting (Fit) - HP -20S Owner's Manual

Curve Fitting (Fit)
This program fits x,y-data to one of three curve-fitting models: power,
exponential, or logarithmic. The program calculates the correlation co-
efficient r and the two regression coefficients m and b. It includes
routines to calculate x given a known y and y given a known x.
The program uses R, through Rq.
Power Curve: y = bx m
_-" Exponential Curve: y = be™*
Logarithmic Curve: y =miIn x + b
General Linear Equation: y=mx+b
The program uses a transformation of the curve fit equations into a
general linear form. The (x,y) data pairs are transformed to this linear
form as they are entered into the statistical registers. This allows the
program to use the built-in statistical functions described in chapter 5
to calculate the statistical variables.
Curve Fitting Models and Transformations
Model Equation Transformed Transformed
Equation Data
Logarithmic y =mInx + b |y =minx + b In x, y (x>0)
Exponential y = be™ ny =mx + Inb X, Iny (y>0)
Power = bx™ Ny =minx +Inb|Inx, Iny
(x>0,y>0)
7: Built-in Program Library 105