MATLAB: Do I get negative results when I estimate the reaction rate and the species concentration with the SBIONLINFIT function in SimBiology 3.0 (R2009a)

Question

I have specified the initial estimates for the reaction rate k and species1. I then used SBIONLINFIT to fit my experimental data and estimate k and species1. The results I get back are negative.

Answer 1

This is expected behavior in SimBiology 3.0 (R2009a). The final estimates for the parameters that are fitted are log transformed in the 'results' - a structure outputted by SBIONLINFIT. To get the actual values for the parameters, take an EXP of the field 'beta' in the 'results' structure (you might need to export 'results' structure to workspace if you were using Simbiology Desktop):

beta=exp(results.beta)

For more information on the SBIONLINFIT used in the individual fitting refer to the documentation by executing the following in the MATLAB command line:

doc sbionlinfit