Smoothing spline

The dialog Smoothing spline is used to perform the settings for plots of smoothing spline functions. Setting of the spline's degree and calculation of its coefficients corresponding to a fit to a data set of an array is done using the dialog Smoothing spline fit, which can be opened by Fit from the Edit menu.

In the group Output by a combobox it can be selected whether the spline function itself, one of its derivatives, or its integral should be plotted. In case of an integral in addition a Lower boundary can be set, i.e. the x value at which the integral is zero.

The limits for the function's argument are entered using the fields xmin and xmax. With Δx the step length for the argument is set. A value of 0 results in automatically dividing the range from xmin to xmax into 100 intervals.

The x and y values can be shifted in the presentation by entering x shift and y shift values.

Factors for x normalization and y normalization may be entered manually. These factors also may be determined automatically using Autoscale with checked Normalization in the dialog Frame.

Markers (Symbol <= 0) or lines (Symbol > 0) may be chosen to present the function. This is done most convenient using the dialog Lines and Markers, to be opened with the button right to the spin box, showing the actual representation.

The Size of lines or markers may be chosen as an additional individual factor to the global setting of the corresponding frame item.

The Color of lines or markers may be chosen using the dialog Select Color, opened with the colored button.

By choosing a Fill pattern the polygon given by the points of the spline function can be filled with a solid color or a pattern instead of being represented by lines or markers.

The dialog Roots for finding roots of a cubic spline or of its derivatives is opened by use of the button Roots.

A table containing the represented values may be exported as a data file by use of the button Export. A file selection dialog will be opened for this purpose.

The dialog may be canceled without saving by use of the button Cancel. By using Apply changes are saved without closing the dialog. With OK changes are saved and the dialog is closed.