MATLAB Open curve fitting toolbox (cftool). The Curve Fitting app provides a flexible interface where you can interactively fit curves and surfaces to data and view plots. You can: Create, plot, and compare multiple fits. Use linear or nonlinear regression, interpolation, smoothing, and custom equations. View goodness-of-fit statistics, display confidence intervals and residuals, remove outliers and assess fits with validation data. Automatically generate code to fit and plot curves and surfaces, or export fits to the workspace for further analysis.