Fityk

Fityk is a curve fitting and data analysis application, predominantly used to fit analytical,bell-shaped functions to experimental data. It is positioned to fill the gap between general plotting software and programs specific for one field, e.g. crystallography or XPS. Originally, Fityk was developed to analyse powder diffraction data. It is also used in other fields that require peak analysis and peak-fitting, like chromatography or various kinds of spectroscopy. Fityk is distributed under the terms of GNU General Public License, but since version 1.0.0, subscription is required for downloading binaries. It runs on Linux, macOS, Microsoft Windows, FreeBSD and other platforms. It operates either as a command line program or with a graphical user interface. It is written in C++, using wxWidgets, and providing bindings for Python and other scripting languages. (Wikipedia).