Keywords:
curve fitting, error propagation, non-linear regression, multivariate, 2D 3D graph, confidence band, basic statistics, least squares, extrapolation, chi-square, correlation coefficient, covariance matrix, graph and plot digitizer (digitizing).

Description:
The LAB Fit is a software for Windows developed for treatment and analysis of experimental data. At LAB Fit you are able to:

1) Treat similar data;
2) Treat non-similar data;
3) Determine propagated error;
4) Plot 2D and 3D graphs;
5) Execute calculations (system of equations, roots of function, etc);
6) Extract data (x;y) from a 2D graph (digitizing with "xyExtract Graph Digitizer");
7) Curve Fitting (almost 500 functions at the library, with 1 or 2
      independent variables, functions finder, etc).

The LAB Fit has a menu for curve fitting and the main programs of this menu use nonlinear regression. The LAB Fit fits functions of one and several independent variables (from 1 up to 6), admitting uncertainties at the dependent variable (Y) and also at the independent variables (X). In case of uncertainties in X and in Y it's made a pre-fit not considering the uncertainties in X, that later on are transferred to Y by error propagation. At the LAB Fit library there are more than 200 functions with 1 independent variable and almost 280 functions with 2 independent variables. The user disposes of a finder functions program. If necessary, there is an option so that the user can write its own fit function. Once determined the fit parameters, it's possible to extrapolate the fit function and, for the 2D and 3D cases, the graph of the obtained function is shown. For the 2D case, beyond the extrapolation possibility, the user can even include error bar and confidence band to the graph. The LAB Fit has also a menu destined to the treatment of similar data, non-similar data and error propagation. Beyond that, there is a third menu with general tools like to plot a function informed by user and many other types of calculations.

And more: the LAB Fit (V 7.2.22 and later) has a reading option used for to extract data from a 2D graph (orthogonal and nonorthogonal axes) contained in a graphic file (scanned, PDF document or in a some file like gif, jpg, etc). The graphic file must be saved in a bitmap file. Then, the "xyExtract" reading option converts the graph back to xy data file.