Fityk is an open source app for nonlinear fitting of analytical functions (especially peak-shaped) to data (usually experimental data).
Fityk is specialized in fitting peaks (bell-shaped functions like Gaussian, Loretzian, Pearson 7, Voigt) to experimental data. There are also people using it to remove the baseline from data, or to display data only.
Fityk is reportedly used in crystallography, chromatography, photoluminescence and photoelectron spectroscopy, infrared and Raman spectroscopy, to name but a few.
Fityk knows about common peak-shaped functions (Gaussian, Lorentzian, Voigt, Pearson VII, bifurcated Gaussian, EMG, Doniach-Sunjic, etc.) and polynomials. It also supports user-defined functions.
Fityk offers intuitive graphical interface (and also command line interface), various optimization methods (standard Marquardt least-square algorithm, Genetic Algorithms, Nelder-Mead simplex), equality constraints, modelling error of x coordinate of points (eg. zero-shift of instrument), handling series of datasets, automation of common tasks with scripts, and more.
Fityk is free and works under Mac OS X, Linux, FreeBSD, and MS Windows.
- covariance matrix and standard errors are calculated using MPFIT library
- GUI: added menu Session > Recent Scripts
- simplified fitting (so that using external libraries is easier):
- removed stopping criterium based on iterations. The max. number of WSSR evaluations can be used instead.
- removed fit continuation (fit +N)