Expression elements are probably the most common function element that you will use in your models.
The properties dialog for an Expression element A function element that produces a single output by calculating user-specified mathematical expressions. looks like this:
The properties dialog for an Expression is very simple, and is almost identical to that of the Data element An input element intended to represent constant inputs in a model.. Other than the ID and Description, there is only a single input field. Expressions are intended for input of a mathematical expression into this field.
Note: You could, of course, just enter a number when defining an Expression. In such a case, however, it would be clearer to someone viewing your model if you used a Data element for that. Doing so helps to make your models more transparent, since the Data symbol will visually indicate to anyone viewing the model that the element represents a constant, and the Expression symbol will visually indicate that the element represents a mathematical expression. If you have entered a number into an Expression element, you can easily convert the element to a Data element by right-clicking on it, and selecting Transform to Data. However, when you do so, if the Expression element was an array A collection of variables that share common output attributes and can be manipulated in GoldSim elements or input expressions., the data will not be preserved when you convert it to a Data element.
Note that the input field for an Expression (the "Equation") is always expanded to several lines to better accommodate and display large equations.
Expression elements have a single output, which can be a value or a condition, and can be specified as a scalar An output consisting of a single value or condition., a vector A one-dimensional array. or a matrix A two-dimensional array.. You can specify these attributes by pressing the Type... button. By default, a new Expression element is a scalar, dimensionless value.
The browser An alternative view of a GoldSim model, in which elements are displayed in a tree, and organized either hierarchically, or by type. view of an Expression element shows a single input (referred to as the Definition), and a single output:
Note: Element inputs and outputs are only shown in the browser if you choose to Show element subitems (accessed via the browser context menu by right-clicking in the browser).
An example model which uses Expression elements (Expression.gsm) can be found in the General Examples folder in your GoldSim directory (accessed by selecting File | Open Example... from the main menu).