![]() Statistical : the weighting coefficients are calculated as the square-roots of each data point in the fitted curve. You must add Y-error bars to the analyzed curve before performing the fit. Instrumental : the values of the associated error bars are used as weighting coefficients. In this second tab you can also choose a weighting method for your fit (the default is No weighting ). Figure 3.11. The second step of the Fit Wizard dialog box. You have to give initial guess for the fitting parameters. The second step is to define the parameters for the fit. Figure 3.10. The first step of the Fit Wizard dialog box. Then you need to define the parameters which have to be fitted in a comma separated list. You can write you own mathematical expression or add expressions obtained with the function selector. If you want to define your own function, you can use the bottom half of the dialog box. To choose one of these functions, you just have to select it and to click on the checkbox under the selector. Four types of functions are available: the user defined functions which have been saved, the classical functions proposed by SciDAVis in the analysis menu, the simple elementary built-in functions, and external functions via pluggins. The top of the dialog box is used to choose a function among the one which are already define. ![]() Then, you need to remove the old fitted curve and to redo the fit with the same function and the new points. If the data points are modified, the fit is not re-calculated. The fitting is done by minimizing the least square difference between the data points and the Y values of the function. This Command is used to fit discrete data points with a mathematical function. In the latter case, this command first creates a new plot window using the list of selected columns in the table. ![]() ![]() This function can be accessed by the Fit Wizard command of the Analysis-plots menu when a plot is selected, or the Analysis-tables menu when aa table window is selected. A set of simplified fitting dialog boxes for most used functions like exponential growth or decay, etc. A general Fit Wizard which allows to use complex functions and to adjust the fitting parameters. ![]()
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