Use the integrate function to operate on a previously saved X–Y data object (a collection of ordered pairs) to produce a new X–Y data object. The new X–Y data object has the same X-coordinate values as the original X–Y data object, but new Y-coordinates are computed as the numerical integral (using the trapezoidal rule) of the original Y-coordinates.
Figure 29–10 shows an example of an X–Y plot produced using the integrate function.
To integrate an X–Y data object:
Locate the Operate on XY Data dialog box.
From the main menu bar, select Tools
XY DataCreate. Click Operate on XY data in the dialog box that appears; then click Continue. The Operate on XY Data dialog box appears.
From the Operators listed, click integrate(X).
The integrate function appears in the expression window.
From the XY Data choices, click the name of the X–Y data object on which to operate and click Add to Expression. You can choose from all X–Y data objects previously saved within this session (listed alphabetically in the XY Data field).
The X–Y data object name appears within the integrate function parentheses in the expression window.
To continue to build your expression, position the cursor in the expression window and type in or select the functions, operators, and X–Y data you want to include.
To evaluate and display your expression, click Plot Expression.
To save your new X–Y data object, click Save As and then provide a name in the dialog box that appears.
Saving your data object makes it available for future operations within this session and for inclusion in X–Y plots containing multiple data objects.
When you are finished, click Cancel to close the dialog box.
