(Comp.sys.hp48)
Item: 416 by oss at itnvax.cineca.it [Stefano Oss]
Subj: polynomial fitting with 48sx
Date: Thu Dec 19 1991

  I am proposing here a simple application for the HP48SX calculator.
The program is intended to be used for obtaining a polymomial (any
reasonable degree) of a given set of X-Y data with graphical
output. The program consits of the following procedures:

MINA, MAXA       find the minimum (maximum) of a given vector;
ROCO             performs the break-up of a given matrix in its rows;
PLTF             gives a graphical representation of both X-Y set
                 as small crosses and the fitting polynomial;
POLF             computes the fitting polynomial in a least squares
                 sense and the standard chi-square number (equal
                 weights).

In order to run this program it is simply needed to input the X-Y
data set in matrix form.  For N data a 2 rows N columns matrix will
be entered in the stack.  Then the requested polynomial degree is
inserted and the POLF procedure is called.  On the LCD screen the
graphical output will appear together with the chi-square value.
After pressing the ON key an algebraic equation (stored in POL)
containg the least squares fitting polynomial will appear.
The program is extremely simple and it can be of course changed in
its many parts in order to improve its possibilities.  It should be
considered only as a little application.  A working one, anyway.
Comments and/or suggestions are really welcome !
                                                    Stefano Oss