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ObjVal = objfletwell(Chrom, P1, P2)

OBJective function after FLETcher and PoWELL This function implements the function after Fletcher and Powell and a discretization of this objective function. The function after Fletcher and Powell is highly multimodal and a representative of nonlinear parameter estimation. For the computation of this objective function two random matrices A, B and a random vector alpha are used. Therefore the function is not symmetric and the extrema are randomly distributed over the search space. The random values of A, B and alpha are retrieved by the private function getFletwellData. This function was first introduced by Fletcher and Powell in: Fletcher, R. and Powell, M.J.D., A rapidly convergent descent method for minimization. Computer Journal, 6:163-168, 1963. In connection with Evolution Strategies the function was used in: Schwefel, H.-P., Numerische Optimierung von Computer-Modellen mittels der Evolutionsstrategie, volume 26 of Interdisciplinary Systems Research. Basel: Birkhaeuser, 1977, pp. 327-328. Baeck, T., Evolutionary Algorithms in Theory and Practice. New York-Oxford: Oxford University Press, 1996, pp. 143-144. Syntax: ObjVal = objfletwell(Chrom, P1, P2) Input parameters: Chrom - Matrix containing the chromosomes of the current population. Each row corresponds to one individual's string representation. If Chrom == [NaN xxx] or Chrom == [NaN xxx yyy], then special values will be returned, see Output parameters xxx == 1 (or []) return boundaries xxx == 2 return title yyy == 0 return title of continuous variant yyy == 1 return title of discrete variant xxx == 3 return value of global minimum P1 - (Optional) Number indicating which variant is used, if Chrom is not NaN or []. P1 = 1 use discrete version P1 = 0 use continuous version If P1 is omitted or P1 = [] the discrete version is used (P1 = 1). P2 - Additional parameter Output parameters: ObjVal - Column vector containing the objective values of the individuals in the current population. if called with Chrom == [NaN xxx] or Chrom == [NaN xxx yyy], then ObjVal contains xxx == 1 (or []), matrix with the boundaries of the varaibles xxx == 2, text with the title of the function yyy omitted: title of continuous variant yyy = 0 title of continuous variant yyy = 1 title of discrete variant xxx == 3, value of global minimum Examples: % continuous variant of the function after Fletcher and Powell >> objfletwell(Chrom) % discrete variant of the function after Fletcher and Powell >> objfletwell(Chrom, 1) Author: Hartmut Pohlheim History: 08.11.99 file created

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