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Expressions
An expression is a mathematical equation, made of up keywords (or operands), operators, and functions. Expressions are used throughout M2Assistant to provide values to be plotted, display hints, determine the color for various network elements, and to filter which network elements are to be displayed. There are seven main types of expressions; filter expressions, label expressions, hint expressions, value expressions, color expressions, column expressions and matrix expressions.
An expression may also contain a description, or comment, which makes it easier to read or understand the expression. The description must be enclosed in square brackets [] and must be at the beginning of the expression. For example, the expression
[Boarding Passengers at I-Node] board
calculates the number of boardings at the I-Node of a segment (using the keyword "board") with a description prefacing the keyword.
The type of expression result can be a number (real or integer), logical value (true or false), or a string. You may use expression functions to convert the result from one type to another in order to obtain the desired result.
Expressions are entered into combo-boxes that are shown in the layer Properties tabs. If you double-click the combo-box, the Expression Editor is displayed. This editor is useful to create, modify and delete expressions.
