The art of model fitting to experimental results

Keeping the simple easy, making the complex feasible, and getting the impossible within reach.

About us

fitteia is a web-based fitting platform committed to providing a high-quality and user-friendly fitting environment to its users. fitteia provides a set of graphic user interfaces that are accessible through the internet by using any web browser of your choice (e.g. IE, Opera, Firefox, Safari, Chrome, etc.).

The fitteia platform allows:

  • Graphical representation of experimental results and/or mathematical functions.
  • Numerical fits to arbitrary (user-defined) linear and/or non-linear functions depending on m fitting parameters and n experimental variables.
  • Data treatment through an integrated programmable calculator.
  • To use an integrated Matlab-like calculator.
  • To write professional-quality reports using LaTeX.
  • Production of documents in PDF, PNG, JPG, and EPS formats of fitting results.
  • User registration through email/password security process assuring the user's privacy.
  • Sharing of working areas with other fitteia users.
  • Sharing of user-defined fitting functions/fitting models, and documents/projects with other fitteia users.
  • The possibility of using three different expertise levels (e.g. Basic, Advanced, Expert).
  • To Select Save/Recover your results.
  • Downloading/Uploading the configuration/setup files.
  • The assignment of two levels of user privileges.

Register through one of the mirror sites

About the etymology of fitteia

fitteia [fɪt.tɐjɐ]

is a combination of two words: fit, and teia. The former is an English word which means to be compatible; in agreement with; match. The latter is a Portuguese word for web; fabric. Together they would "translate" to "fit on the web" or "fit on the internet".

The word fitteia is also associated to the desire of providing a "fitting environment" interface for all.

About fitteia®

fitteia is a trademark of Instituto Superior Técnico registered with INPI, nº 498461

About the system

fitteia integrates a set of different programs written in C and PERL that run on Debian Linux. Services: MySQL, APACHE, the MINUIT CERN lib routine and LaTeX are required. The least squares minimization is performed by a compiled C program that interacts with the user through a set of Perl scripts. All together the fitteia environment allows the user to perform high level model fitting and plotting tasks, avoiding the overhead work of dealing with micromanagement of basic data files, plots, source code functions, file sharing, etc..

The development of fitteia doesn't follow a conventional software project model which are designed for a specific purpose and a goal. Instead, it was started in 1990 to solve fitting problems related to NMR relaxation, at a time when there was no internet, Windows 3.0 was released, and Linus Torwalds was still developing Linux. fitteia has been continuously evolving since 1990. Here are some dates and milestones:

  • 1990-1993: C kernel code for VAX and Unix operating systems: gfitn - fit N functions with P parameters to M points, for arbitray values of N, P and M with global least squares minimum target.
  • 1993-1996: intensive testing and consolidation of the main high level fitting and ploting unitary tasks
  • 1996-2000: Text based interface and graphical user interface for X11 running in Unix/Linux
  • 2000-2004: Integration of CVS in fitteia and standalone KNOPPIX versions: OneFit
  • 2004-2009: Development of the fitteia environment: Perl Common Gateway Interface (CGI) modules that interoperate with the gfitn kernel.
  • November 2009 fitteia is made available for users

fitteia celebrated its 10th anniversary in 2019

10 years: 22,500 users; 113,000 sessions, 2,070,000 pageviews; 113 countries.

Anniversary logo


fiiteia it the result of a search for a solution to a model fitting problem, the pleasure of software programing, a series of stimulus and challenges, some curiosity and preserverence, and a pinch of generosity.

Pedro José Sebastião wishes to thank in particular: António C. N. Ribeiro, Carlos Cruz, José Esteves, António Amorim, Antonio Ferraz, Friedrich Noack, Mika Vilfan, Heinz Gotzig, Daniel Guillon, Yves Galerne, João Figueirinhas, Alberto Ferreia, João Godinho, Tomaz Apih, Anton Gradisek, Luís Gonçalves, Carlos Varandas, Horácio Fernandes, and Gregory Svern.

A word of thanks to all MEFT students at IST that have been using fitteia in the past 10 years.

Finally, many thanks for all the programmers that have been contributing to the development of Linux, and Debian, FSF, and GNU, and to the open source software movement.

About fitteia's supporters

fitteia was developed interelly without any specific finantial support.

Nevertheless, we must acknowledge the implicit support of the Instituto Superior Técnico for the fitteia@ trademark and for hosting the two running virtual servers and this webpage, KIC and STELAR for promoting fitteia.