Custom Function (2D Graphs)

These options are available in the Custom Function dialog box and via the Graph Options dialog box, and are used to modify or delete an existing custom function or add a new one to the current plot.

Function/Add new function/Delete. A drop-down list of functions in the current graph is displayed in the Function section. To edit an existing plot, select the plot number and use the options described below. If no functions are available or you want to create a new function, click the Add new function button. To delete an existing function, specify the function number in the Function field and click Delete.

Definition. Use the options under Definition to define the function.

Type. Select either a function or a parametric curve.

Add to list. If you want to create a function that can be saved and reused at a later time, click this button. The Custom Function Name dialog box will be displayed, in which you can specify a name for the function. The function can then be selected from the Function Name Manager and edited (see Function list).

Function list. Click this button to display the Function Name Manager, which is used to create a new function and to edit, rename, or delete an existing function.

Function guide. Select the Function guide check box to display a list of possible function and related properties when you enter a custom function into the box directly below this option.

Y, Y(t), X(t). Type the function you want to plot in the Y box. If you are defining a parametric curve, specify Y(t) and X(t) in the appropriate fields. Note that if you have selected the Function guide check box, a menu with possible characters or functions will be displayed as you type. You can choose from any item on the menu, or type the function yourself. If you want to save this function for later use, you must add it to the function field in the Function Name Manager. It will not be automatically added for you.

Use event handler calculations. When a custom function handler is attached to the graph, you can use either the custom function calculations as defined in the event handler or enter the custom function in the Y box [or Y(t), X(t) boxes for parametric curves]. To use the custom function calculations, select the Use event handler calculations check box. The Y [Y(t), X(t)] boxes will be dimmed and the custom calculations will be applied. When this check box is cleared, you must enter the custom function in the edit boxes. Note that this option is only enabled when a custom function handler is attached to the graph. For more information on creating custom functions, see the SVB example on Creating User-defined Custom Functions.

Range of X, Range of parameter. Specify here the range (i.e., minimum and maximum values) for the custom function. You can either base the range on the current axis (select From axis for both the minimum and maximum values), or you can specify a custom range (select Custom for both values). Note it is possible to select From axis for one and use a Custom range for the other (e.g., From axis for the Minimum and Custom for the Maximum). If you choose a Custom range, specify the Minimum and/or Maximum value in the appropriate Value field.

Line. The options under Line determine the shape, size, color and resolution of the custom function line.

Pattern. Select the Pattern check box if you want to have a line for the custom function. You can customize the appearance of the line in the Line Properties dialog box, which is available by clicking the Pattern button. The current specifications for the line will be shown in the view box on the Pattern button.

Resolution. Select an option from the Resolution list to control the resolution of the fitted function in the graph. Once the fitted function has been determined, the fit is approximated by points on the x-axis. To control the resolution, you can approximate the fit with a small number of points: 200 (select Normal); a large number of points: 12800 (select Perfect); or somewhere in between [select Medium (400 points)], High (800 points), or Very High (3200 points)]. Selecting a higher number of points will result in a smoother appearance of the fitted function in the graph; however, selecting a higher number of points will also slightly slow down the graphing procedure.

Note that the default (Normal) setting will produce smooth function lines in most cases; the higher settings will make a difference only when you either zoom in on part of the graph or use logarithmic scaling (to "stretch" a part of the scale).

Assignment of axis. For both the X and Y axis, you can specify the assignment of the custom function to a specific axis. The function will then be plotted against that axis. If you select Y axis, you can either assign the custom function to the Left, Right, or Custom axis. If you select X axis, you can either assign the custom function to the Top, Bottom, or Custom axis. Note that if a custom axis is not being used in the graph, the Custom option button will be disabled. Additionally, assigning the custom function to the Top or Right axis when neither axis is being used in the graph, will not automatically cause scale values to appear on that newly assigned axis. To edit or add scale values, use the Scale Values tab or dialog box.

Style. Instead of specifying line patterns in the Line box, you can select the style you want to use for this line from the Style drop-down box. To view a menu of options related to styles (Save, Save As, Revert to unmodified, etc.), click the button to the right of this box. For more information on styles, see Graphics Styles.