![]() ![]() There are special operations to do this, and they are discussed in chapter Sets as Sequences: Ordered Sets. However, if the members represent, for example, time periods, then it may be useful to refer to the next or previous member. The order in which the set members are listed is usually not important. Note that each element in a set must be separated from other elements by a comma or by an end-of-line, and each element is separated from any associated text by a blank.Ĭonsider the following example from the Egyptian fertilizer model, where the set of fertilizer nutrients could be written as Set cq "nutrients" / N, P2O5 / Element is the name of the set element(s). ![]() The list of set elements is delimited by forward slashes. The optional explanatory text may be used to describe the set or a specific set element for future reference and to ease readability. Set_name is the internal name of the set in GAMS, it is an identifier. Set is the keyword that indicates that this is a set statement. In general, the syntax for simple sets in GAMS is as follows: set set_name They are labels, but are often referred to as elements or members. The set statement begins with the keyword set, S is the name of the set, and its members are a, b, and c. Using GAMS notation, the same set is defined in the following way: Set S / a, b, c / Using common mathematical notation, a set \(S\) that contains the elements \(a\), \(b\) and \(c\) is written as: The chapter will be concluded by a topic on domain checking, a very important feature of GAMS, and a section about Domain Defining Symbol Declarations. We will introduce simple sets, subsets, multi-dimensional sets, singleton sets and the universal set. The topics discussed in this chapter will be enough to provide a good start on most models. More advanced set concepts, such as assignments to sets, and lag and lead operations are covered in the chapters Dynamic Sets and Sets as Sequences. In this chapter we will introduce how sets are declared and initialized. They allow the model to be succinctly stated and easily read. Sets are fundamental building blocks in any GAMS model. ![]()
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