(25) Resolution of the Catch Equation by a Simple Iterative Method

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An extract from Resolution of the Catch Equation by a Simple Iterative Method, Institut Scientifique et Technique des Pêches Maritimes, ICNAF Res. Doc. 78/VI/19, JUN 1978.

Abstract
The solution (F) to the catch equation when catch and population size in numbers are known is determined quickly and accurately using NEWTON's iterative method on a pocket calculator. The method and program are discussed …
Expression (5) is very easy to program and compute on simple programmable pocket calculators …
Two solutions can be included in the program: either a large initial F is systematically entered to start all of the iterations, or a test of the sign of F is included in the program to eliminate the negative root automatically and return to the iterative step …
A typical listing of this program for HP programmable pocket calculators is presented in Table 1. Depending on the model of calculator used, all or parts of the program may be performed automatically …
With the model HP-25 calculator used by the author, parts (2), (3) and (5) are performed with the program, while parts (1) and (4) must be done manually, but the whole computation is possible in a single program with models HP-29 or HP-67. The program occupies a small number of program steps and a small amount of memory.

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ps: see also (HP-65) A Simple Iterative Solution to the Catch Equation