Fityk

fityk is a program for nonlinear fitting of analytical functions (especially peak-shaped) to data (usually 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. Fityk also supports user-defined functions.

Fityk offers intuitive graphical interface (and also command line interface), variouse optimization methods (standard Marquardt least-square algorithm, Genetic Algorithms, Nelder-Mead simplex), equality constraints, automation of common tasks with scripts What's New in This Release: [ read full changelog ]

· manual was converted from DocBook to reStructuredText
· GUI: On Linux fitting was very slow, this was fixed. A new option `refresh-period` was added to control refreshing during fitting.
· define supports variable substitution with "define ... where ...", e.g. define Foo(alpha) = alpha * eta * (eta / tanh(eta) - ln (2*sinh(eta))) where eta = 2*pi/alpha * sin(theta/2), theta=x*pi/180
· added access to symmetric errors from scripts (e.g. $variable.error or %func.height.error)
· category "Education" was added to fityk.desktop