Parameter

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A constant in a mathematical program, not subject to choice in the decision problem, but one that could vary outside the control of the decisions. Examples are supplies, demands, loss factors, exponents and coefficients in polynomial functions (of the decision variables). Not all coefficients are parameters, as many are zero by the logic of the model. For example, the only data for a standard transportation problem are the costs, supplies and demands. These can depend upon parameters, but the LP matrix does not – it is the incidence matrix of the network. In general, parameters are data-dependent constants, rather than logically fixed for all instances of the model. Some parameters are simply units of measurement, such as the amount of energy (Btu) in a ton of coal, whereas some parameters are uncertain, like demand for a product.


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