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(41C) Data Fitting by analytical function
06-19-2019, 11:51 AM
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(41C) Data Fitting by analytical function
An extract from HP-41 Calculator Programs for Fitting of Data by an Analytical Function, U.S.DoE (materials sciences - basic energy sciences), UoC Berkeley (chemistry), LBL-15346, December 1982 (87 pgs.)

The general availability of programmable calculators and computers has signaled a shift from the tabular presentation of thermodynamic data to Is presentation in the form of analytical equations and the replacement of graphical methods of treating data by analytical methods. HP-65 and HP-67 calculator programs for a variety of thermodynamic calculations have been presented in two earlier reports. The present report lists programs for the HP-41c calculator which are of particular use in representing thermodynamic data in analytical form.
The first section will deal with analytical equations for interpolation purposes. The equations are fit to two, three, or four tabulated points …
The second section deals with fitting -(G°-H°)/RT values or other quantities tabulated for a large number of evenly spaced temperatures. A least-square fit is provided using Chebyshev orthogonal polynomials …
The third section deals with least-square fitting of sets of x,y values to an equation for f(y) …
The initial sections give the directions for using the calculator programs and the steps of the program are listed along with use of the storage registers. In an appendix, a more detailed discussion is given in regard to the reasons for the procedures used and operation of the program. Possible modifications of the programs for special purposes are also listed.

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