Configure

The page Basic settings is used to perform basic presettings.

In the group Page format the size of the plot page may be selected using the combobox. The setting  Custom allows to set user defined Width and Height values.

In the group Default colors the preselections of the colors for  Frame, Grid, and Data may be performed. Selection is done in the dialog Select Color, opened with the colored buttons.

The presetting of the Decimal symbol for reading data files can be chosen to be point or comma.

In the group Output format, the double value Presentation and the Precision for function parameters and ranges in output files and dialogs may be set, corresponding to the format identifier of the C function printf(). The separator char used to separate columns in exported data files can be selected using the combobox  Separator. Space, tab or comma characters may be selected.

Also the toggle options of the Settings menu can be set here at once.

When Autofit is checked, an automatic parameter fit will be performed after loading the data file, corresponding to the settings performed on the  Autofit settings page.

When Use multiple cores is checked on machines with more than one CPU, all CPUs will be used for parallel computation of function values for plots and parameter fits.

The page Autoplot settings is used to perform the settings for automatic scaling of data files loaded by command line parameters, file menu, or by drag and drop.

In the group Axis mode one can choose between only a frame around the data window or additional tick marks on the left and lower sides of the frame or a grid. tick marks and grid may be labeled with numeric values.

In the group Window position and size of the data window may be set.

In the group Labels text for the axis labels and a heading may be entered. Text with special characters is entered most conveniently in the dialog Edit text which shows up when using the buttons right to the entry fields. By checking = path the path of the data files is used as the heading label.

In the group Data the file columns for abscissa and ordinate values may be chosen by x column and y column. 0 corresponds to the first column. Logarithmic scaling can be selected individually by checking log. When Error bar is checked, the column chosen by Error column is used for displaying error bars. When Normalization is checked, powers of ten are evaluated to be multiplied with the numeric data values in case of huge or tiny numbers. If not equal to 1, these normalization factors are included in the axis labels.

In the group Representation the presentation of the array data is set. Data may be presented by markers ( Symbol <= 0) or lines (Symbol > 0). Most conveniently this is selected in the dialog Lines and Markers, opened by the button right to the spin box, showing the actual representation. With Symbol size the relative size of characters and markers as well as the relative line widths (proportional to the width of the data window) may be specified. A setting of 100 % corresponds to the default. By choosing a Fill pattern the polygon given by the points of the array can be filled with a solid color or a pattern instead of being represented by lines or markers.

The page Autofit settings is used to perform the settings for automatic parameter fits of functions to data sets, which are combined with the autoplot feature when the option Autofit is activated in the Basic settings.

In the Library field in the group y(x) the path of the shared library containing the function to be fitted may be entered. The button right to the entry field opens a file selection dialog for this purpose.

The name of the Function is entered in another field. The function may be chosen from a list in the dialog Functions, opened with the button right to the entry field.

With the button Edit a dialog Parameter may be opened, which allows to enter the values of up to 20 initial parameters of the function. Also the parameters which should be fitted and not kept constant may be selected by checkboxes. When the option  Show Function Source is activated in the Settings menu and a C or C++ language source file with the same name as the shared library but the extension  .c or .cpp, respectively, is present in the same directory, its contents is displayed right to the parameter fields, too. The button  Load opens a file selection dialog for loading the parameters from an text file (one parameter each line). The button Save opens a file selection dialog for saving the parameters in an text file.

When the box Nonlinear fit is checked, nonlinear parameter fits by employing the iterative Levenberg-Marquardt method will be performed. Otherwise noniterative general linear least square parameter fits are selected. In this case the function must depend linearly on all parameters chosen to be fitted.

When the box Error column is checked, the corresponding column of the data set, selected on the dialog page Autoplot settings, will be used as the standard deviation of the y values for calculation of chi-square. Otherwise the standard deviation will be estimated by an error model function taking the x or the y value as its argument. This function and their parameters may be selected in a dialog which is displayed by clicking Model. A simple error model might be selected by choosing a polynomial with p1 = 0.01, resulting in standard deviations of 1 %.

Termination of the iterative nonlinear parameter fit algorithm may be controlled by setting a Maximum iterations number and a Tolerance value. Fitting will be terminated when either the maximum number of iterations is reached or the relative errors of chi-square or of the parameters have decreased down to the tolerance value.

When Show dialog is active, the dialog Parameter fit is shown when performing the fit, allowing monitoring and interaction.

The resulting parameter settings will be saved automatically on disk, when the option Save parameters is active. The filename is derived from the name of the data file. The extension is set to .par.

When Follow parameters is active, the set of initial parameters will not be reset before starting a fit to the next data set of a series of data files.

In the group Representation the presentation of the fitted function is set. It may be presented by markers ( Symbol <= 0) or lines (Symbol > 0). Most conveniently this is selected in the dialog Lines and Markers, opened by the button right to the spin box, showing the actual representation. 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 function values can be filled with a solid color or a pattern instead of being represented by lines or markers.