NAG Library edition of Simfit

More about NAG in Education

To learn more about NAG in Education, click on one of the following links or contact us to discuss your needs.

NAG routines add extensive new functionality to Simfit

The academic version of Simfit is a free Windows package for simulation, curve fitting, statistical analysis and graph plotting developed by Bill Bardsley, University of Manchester, UK. It employs mathematical models from a compiled library, or from user-supplied equations, and can be used in many fields of study such as biology and psychology, and areas of work such as growth curves, factor analysis, power as a function of sample size, dose response curves, and pharmacokinetics.

At present, the NAG Library edition of Simfit uses nearly 200 numerical algorithms from NAG, and is currently being extensively enlarged in the computational areas of optimization, differential equations, curve fitting and statistics. The DLL implementation of the NAG Fortran Library is the source of the NAG algorithms used by Simfit as opposed to the public domain code used by the academic version, and this is permitting a rapid extension of Simfit functionality.

Higher performance implementation of BLAS and LAPACK
The runs up and down test for randomness
The median test
The Mood and David tests for equal dispersions
The Kendall coefficient of concordance
After calculating distance matrices, classical metric scaling (principal coordinates) and non-metric scaling (calculation of STRESS and SSTRESS functions) can be done
Multivariate factor analysis is provided
Procrustes analysis can be performed on two loading matrices
Varimax or Quartimax rotation can be performed on a loading matrix
Kernel density estimates can be calculated, and then plotted against sample histograms and cumulative distribution functions
Cross validatory splines can be fitted
IFAIL messages are written to the file nagifail.txt, which can be browsed retrospectively in the case of failure of iterative algorithms to converge and similar problems
There is a mechanism to demonstrate how to use the NAG Library from within the Simfit environment

More about Simfit

The Simfit package consists of some forty programs, each dedicated to a special set of functions such as fitting differential equations or specialized models, plotting, or performing statistical analysis. The package is driven from a program manager which also provides options for viewing results, editing files, using the calculator, printing files, etc. Simfit has been used for many years in postgraduate courses and students often report that it is very easy to use on account of the very extensive on-line help provided in the form of pdf with hyperlinks for easy cross-reference. Most students find they can write their own models and fit their own data within a few hours of being introduced to the package for the first time.

Simfit has wide coverage, great versatility, fast execution speed, and the ability to handle large data sets. It can perform maximum likelihood estimation, automatic calculation of starting estimates, and constrained nonlinear regression. Programmers should note that the source code is distributed with the package, along with the Simdem package, which shows programmers how to write Windows programs that can use the NAG Library.

For more information about the Simfit package, visit the Simfit page hosted by the University of Manchester.