User Function Edit dialog box

UserFnEditDlg

Use this dialog box to create new functions and to modify existing ones.

Here are the steps to create a new user function or to modify existing functions:

You must type a distinct function name in the Identifying Function Name box. This is the name by which the function will be known to Predictive Systems Lab, and as such, it must be unique. There are no particular rules as to what the name should be, or what characters may be used in the name, except that the name must be different from those of existing functions.

It is a good practice to assign significant names to simplify function selection from lists elsewhere in Predictive Systems Lab.

You must type a functional expression for the function in the Function - F(x) box in accordance with the grammar rules discussed in Defining User Functions in Predictive Systems Lab. If the space provided for entering the functional expression is too small, click the

button immediately to the right of the box to display a larger area for typing. You can then use carriage returns in the text to break exceedingly complex functions into more readable parts. To enter carriage returns in this box, press CTRL+ENTER when the caret is positioned at the appropriate text location.

You can copy and paste multi line functional expressions from and to your favorite text editor to the extended Function - F(x) box.

3.	If you will be using this function for operations that require the use of derivatives, you should type the expression for the function's derivative in the Derivative - D(x) box; otherwise, you can leave this box set to the default (zero).

If you know the extent of the function being defined, it is a good practice to type the minimum and maximum values in the Minimum Function Value box and the Maximum Function Value box, respectively. Some operations require knowledge of the extent of a function for scaling. For example, the function SQRT( ABS(x) ) has a minimum value of zero (0), and a maximum of 1.340781e+154 (square root of 1.797693e+308, the maximum 32-bit machine floating-point number representation).

5.	After properly defining the function, you can test it by clicking Test. This action will parse the expressions, and if successful, display the User Function Test dialog box, which allows you to visually inspect the behavior of the function and its derivative.

6.	Click OK to parse the functional expressions, close the dialog box, and save any changes you have made, or click Cancel to close the dialog box without saving any changes you have made.

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