Graphic displays of experimental results facilitate decisions regarding mathematical models which relate experimental results to controlled parameters. Experiments frequently produce response variables which are non-linearly related to the controlled variable. Computer programs can be useful to fit model functions to experimental data. SIMPLOT7, written in Microsoft QuickBASIC, provides graphic display of experimental data and non-parametric fitting of user-defined functions to experimental data. The algorithm utilizes simplex-based non-parametric minimization of residuals, and the user-defined function may contain up to seven parameters to be determined for best fit. Once optimum fit values have been determined, both function and data can be graphed for visual inspection of the result.