A Superior Curve Fitting Computer Program for Functions of Two Variables A superior, interactive, iterative, least squares computer program has been written in PL/1 for the IBM 3701145 with time sharing option, CALL-OS, which minimizes hoth the absolute and relative deviations in the dependent variable in a significant extension of the work reported by one of us previous1y.l Use of the program to fit vapor pressure, temperature data to the four-constant Kirchoff equation demonstrates a significant superiority of the iterative technique used in fitting a limited amount of very precise data for water over the conventional non-iterative method used with or without approximate weighting factors when minimizing either the absolute or relative deviations in the dependent variable, respecti~ely.~ Specifically, use of the usual approximate weighting factors in minimizing the ahsolute deviations resulted in an over-all standard deviation 24 percent greater than that computed with the iterative procedure without weighting factors. The program can he readily adapted to almost any multiple-constant equation in two variables of scientific interest with little difficulty and offers researchers and students the opportunity of re-assessing their own least squares procedures in order to insure the mast accurate mathematical representation of their data. Copies of the program with sample output and a detailed write-up are available from GFPupon request. 'Pollnow, G. F., J. CHEM. EDUC., 48,518 (1971). ZSands, D. E., 3. CHEM. EDUC., 51,473 (1974). JNow a graduate student a t the Institute of Paper Chemistry, Appleton, Wisc. Gilbert F. Pollnow University of Wiseonsin-Oshkosh Michael J. Vander Wielen3 Oshkosh, 54901
Volume 52, Number 8. August 1975 / 543
