# Converters

Purpose: The converter serves a utilitarian role in the software. It holds values for constants, defines external inputs to the model, calculates algebraic relationships, and serves as the repository for graphical functions. In general, it converts inputs into outputs. Hence, the name "converter."

Selection and Placement:

- Select the converter icon by clicking once on the circle icon in the Building Block palette. [Note that the drop-down list also enables you to select a special type of converter called the summer converter.]

- Move the mouse to the desired location.

- Click once to deposit the converter.

Surface Operations: Figure 4-18 details surface operations which may be performed on a converter.

Figure 4-18 Converter Surface Operations

Mapping Dialog Operations: When you open a converter in the Mapping mode, you'll enter its Mapping dialog. Figure 4-19 details the operations within this dialog.

Figure 4-19 Converter Dialog - Mapping Mode

Modeling Dialog Operations: In the modeling mode, the converter dialog provides a wealth of additional capabilities. Figure 4-20 shows the converter modeling dialog when inputs have been drawn.

Figure 4-20 Converter Dialog - Modeling Mode - Inputs Drawn to Converter

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Summer Converter:

The Summer Converter dialog is only available when there are no inputs drawn into the converter. The summer converter enables you to add together a set of model variables, without the need of drawing inputs to the converter. This special converter type can be exceedingly helpful when you are creating summary report indices and the like. See Figure 4-21.

Figure 4-21 Summer Converter Dialog - No Inputs

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Special Note:
Graphical Functions

The Become Graph button at the lower left of the dialog enables you to define the converter as a graphical function. Graphical functions also may be defined from within a flow dialog. A graphical function is a sketch of a relationship between some input (which itself can be an algebraic relationship defined from the Required Inputs list and/or Builtins list) and an output. Once the input has been defined in the equation box, a click on Become Graph leads you to the graphical function define dialog.

Your tasks within the graphical function dialog are straightforward:

- Set the min and max values for the X-axis. Type numbers within the two fields below the graphical function grid. The number in the left field (the min value) must be less than the number in the right field (the max value). Hit the tab key to move from field to field. The minimum and maximum values you choose for the X-axis will be reflected in the non-editable left column (input), to the right of the axes.

- Set the min and max values for the Y-axis. Type numbers within the two fields to the left of the graphical function grid. The number in the bottom field (the min value) must be less than the number in the top field (the max value). Hit the tab key to move from field to field.

- Set the number of data points. Type a number into the Data Points field, found below the two columns of numbers. You must have at least two data points in a graphical function. You can have up to 1500 data points. When a graphical function contains more than 13 data points, the grid becomes scrollable. To view the entire function, depress the alt key (Windows) or option key (Macintosh).

- Create a relationship. Click-and-hold the cursor within the grid. As you drag the cursor, a curve will be drawn, following your mouse movements. In addition, the Y-axis coordinates of the curve will be displayed in the right column (output) at the far right of the dialog.

Figure 4-22 Graphical Function Dialog

Notes:

- Editing numbers directly: You can edit a graphical function by typing numbers into the right-hand column (the output column). Click on one of the numbers in the output column. The number you select will appear in the Edit Output box. Type the number you want; then hit the tab key on your keyboard. The point you have just defined will appear on the curve, and the next number down the output column will become selected.

- Copy/Paste operations: A graphical function's output column can be copied and/or pasted. To copy/paste data into the output column to/from the clipboard, select a number (or a set of numbers) in the output column (to select the entire column, click once on the entity name at the top). Then, under Windows, type control C to copy, or control V to paste. On the Macintosh, type command C to copy, or command V to paste. The number(s) you select will be replaced by the data you paste. The number of data points will be adjusted to reflect the size of the data set being pasted.

- Data Links from other applications: It is possible to create data links to your model from other applications; these links will be continually updated as changes are made in either application. On Windows, this is accomplished with DDE (Dynamic Data Exchange); on the Macintosh, through Publish & Subscribe. See Chapter 8 for details on DDE and Publish & Subscribe.

- Continuous vs. Discontinuous Graphical Functions: The small button near the minimum boxes enables you to make the graphical function into either continuous or discontinuous line segments. A click on the button will make the line segments discontinuous - a set of flat line segments, as shown in Figure 4-23. Another click will toggle the curve back to the continuous mode. Note that in the discontinuous mode, the last number in the output column is not editable.

Figure 4-23 Graphical Function in Discontinuous Mode