This dialog box is opened when you select the **Integrate Function...** command from the
Analysis menu.

Pressing the *Integrate* button performs a numerical integration
of a user defined analytical function. This function can be entered/edited in the
*Function* text box. The numerical result of the integration is displayed in the
Log Panel.

The Σ button pops-up a menu listing all built-in mathematical functions provided by QtiPlot. Pressing one of the actions from this menu copies the displayed function into the edit box at the position of the text cursor.

Clicking on the button displaying a pencil icon opens a menu which lists recently used functions. By pressing one of the menu items, the selected function is inserted into the edit text box at the current position of the cursor.

Clicking the *Clear* button removes the contents of the
*Function* text box.

The *Variable* input field displays the name of the independent variable of the
function (i.e., the variable of integration). By default it is set to *x*.

The third input parameter is the maximum number of *Subintervals* that the
integration algorithm may use to integrate the function. The default value of 1000 should work in almost
all circumstances.

The fourth parameter is the *Tolerance* limit. Smaller numbers will result in
the algorithm using more subintervals. The default value of 0.01 should work for most functions.

The next two fields are the lower and upper limits of integration. Set these to whatever values you need.

The *Plot Area* option should be checked if you want that QtiPlot
draws a plot of the integrated function on the currently active layer. A table of the plotted data can be
generated by right clicking on the curve and selecting the *Worksheet *command.