Restricting domain of values fzero will try

I am using fzero along with an implementation of the gillespie algorithm to determine a parameter (I know the vale of a parameter at steady state, but now I want it proportional to another quantity, and I am using fzero to determine this constant of proportionality, alpha).

However, the simulation only works if alpha is positive, otherwise we get negative rates which mess everything up. From what I can tell, fzero is trying negative values of alpha when trying to find the zero. Is there any way I can restrict fzero to only use positive values?

Answer 1

[Matt J]

Specify the search interval [xlower, xupper] to include only non-negative values.

fzero(fun,[xlower, xupper])

[Alexander Holmes]

At the moment I have an initial guess for alpha, which I would like to use as the initial value. Is it still possible to have this, and to specify an interval it can't go outside of?

[Matt J]

You could make a change of variables in your function like s^2=alpha. An unconstrained search over s is equivalent to a search of non-negative alpha.

[Alexander Holmes]

Thank you!

Answer 2

[Matt J]

You could make a change of variables in your function like s^2=alpha. An unconstrained search over s is equivalent to a search of non-negative alpha.