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# FunctionFitter

A widget for graphing a parameterized function while exploring parameter variations. Also can adjust the parameters automatically to fit data. Function, parameters, independent variable can be specified by the user. This widget may be saved in a session.

The FunctionFitter starts out with entries for graphing a single exponential with two parameters. When a parameter value is changed the graph is replotted.

## Plot

Replots function with current arg values

## Steps

Number of values of independent variable used in plot

## IndependentVar

Enter the name of independent variable in a string dialog.

## Args

Enter space separated names of parameters in a string dialog. Default value editors for these parameters will appear in the rightmost box.

## Yexpr

Enter an expression involving the independent variable and the parameters (args). Any valid top level hoc expression is acceptable.

## PraxisFit

Starts fitting the function to the data with respect to the DataWeights by adjusting the checked argument values. See `fit_praxis()` .

## StopAtNextQuadForm

Stop the praxis fitter when it finishes its current/next cycle. At this point it contains a computation of the quadratic form of the parameter phase space (printed in the terminal window).

## Running

Checked when the praxis fitter is executing.

## WatchTheFit

Plot the function on each call to the error function during fitting. Things are slower if this box is checked.

## RoughFit

Instead of fitting all the data according to the data weights, use only 5 equally spaced points in each of the two central data regions. Things can be much faster if this box is checked.

## ArgValues

The values of the arguments are used in the plot. When a value is changed the function is replotted. When fit data is present, a checkbox is added to the left of each argument button. When the box is checked then the fitter adjusts the value for a best fit. When not checked the parameter is treated as a constant.

### CurrentValuesAsDefault

Resets the default values of the parameter field editors to their current values.

## FittoData

### ReadDataFile

Get data from a file. The format is the number of data points followed by pairs of x,y data.

### CommonFunctionalForms

### FitCriterion

not implemented

### ParameterRangeLimits

Pops up a panel of parameters with their range limits. When the fitter calls the error function and one of the parameters is outside its range the error function will return a value of 1e6.

### DataWeights

Pops up a panel of data weight intervals and weights. The first interval ranges from the beginning of the data to the interval 1 endpoint. From the interval3 endpoint to the end of the data, the weight is 0. The entire interval is given the weight indicated. Intervals can be manipulated directly by the AdjustWeightRegions tool of the Graph menu.

### SaveRestoreFunction

Arg values and the y-expression can be saved in a list and restored by selection with a browser.

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