Fitters

Java Analysis Studio comes with a least-squares fitter.  Like functions, fitters are stored in a registry and you can add and remove fitters from the registry.  The fitter registry will be saved and loaded next time the application starts if the 'Save registries' box in the 'Defaults' tab of the 'Options' dialog is selected, which it is by default.  To define your own fitter, see the documentation.  See also the section on the default fitter.

There are three ways to fit a curve to data.

• The first way is to select the 'Fit' submenu from the popup menu (when activated on a histogram plot).  The 'Fit' submenu will only be active if there is at least one fittable function that is not fit already and one data set on the selected plot.  If there are multiple data sets, you will first be asked to select which one you want the curve to be fit to.  You will then be asked which curve you want to be fit to that data set.   To look at the parameters of the fit after fitting a curve in this way, you will have to select the 'Functions' tab on the 'Properties' dialog and select the function you have just fit.  The parameters are displayed on a table there.
• The second way is to access the same 'Fit' submenu from the 'Functions' submenu of the 'Histogram' menu.  When a fitter that was executed in these two ways is finished, the chi squared value for the fit will be displayed in the lower left corner of the application frame.  To look at the parameters of the fit after fitting a curve in this way, you will have to select the 'Functions' tab on the 'Properties' dialog and select the function you have just fit.  The parameters are displayed on a table there.
• The third way to fit a curve to data is to select the 'Functions' tab on the 'Properties' dialog, and select the 'Fit' check box.  The check box will only be enabled if a fittable function has been selected.  The new fit parameters visible are on the same pane.

The fitter should stay linked to the data as you have set it and should re-fit the curve each time the data change.  If the function has handles and you move one of them manually, the fit will be cleared and will no longer update with the data.

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Page maintained by Jonas Gifford.   Last updated 01/14/04.