The dialog Roots can be opened using the button Roots of the dialogs Function, Smoothing spline, and Smoothing spline fit. It is used to find roots of the function or spline, respectively, or of its derivatives. In case of a function an interpolating (non-smoothing) cubic spline representation is employed, in case of a smoothing spline the current spline is used; its degree has to be cubic.

The Condition for roots to be searched and displayed can be selected. A constant  c may be used to find points with nonzero values of the spline or its derivatives. The button Update is used to update the displayed list of points after changing the constant c. The Condition can also be set to Minimum or Maximum. Then points with a vanishing first derivative and a positive (minimum) or negative (maximum) second derivative are listed.

The list of points, consisting of columns with their x, y, y', and y" values, can be exported as a text file using the button Export. A file selection dialog will be opened for this purpose.

The dialog is closed by using the button Close.