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Sicyon Lite calculator 4.0 - User Guide and FAQ
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Fitting procedure
To fit a function (an expression or program code model) you have to:
- Enter your expression or code with variables, one for abscissa and the rest - to be fit.
- Set one range variable, which is used only to recognize the abscissa variable; the range itself is ignored and abscissa values are taken from the first column of the data set. Open the Fit module.
- Check the variables you want to vary for best fit and uncheck others. The check mark is @ and double clicks on it. You can edit the values in the Initial Values column as well. The next column will give you fitted values and the last one - the precision of their calculation.
- Below the variable table you can specify the criterion by which the fitting will proceed, it could be either chi-square or sum of absolute distances between fitted and data points. The later is less sensitive to the dropped points (way out of line).
- After entering in the fitting frame for the first time you have to supply the procedure with data (most left button): opening file or paste from clipboard. The file format is simple XY ASCII format with columns separator Tab (ASCII 9) or comma. Semi-column (;) as a first character in a row makes Sicyon skip that line. Sicyon knows how to use point errors if you specify them. So the file could have two or three columns (without or with errors). The fitting procedure would give more weight in chi-square of the points with less error and vice verse.
- Sicyon will draw chart with current curve parameters and data points. The table page gives you more precise (and less visual) information about the same, including the difference between the data and the fitted curve Y-values. The second column of this table is of particular interest. Double click on the symbol @ and you can make certain points be excluded (or included) from the calculations. The data points from the chart will follow, making themselves hollow. You will have the same result double clicking on the data points.
- Click on FIT button and enjoy the view.
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