Search All of the Math Forum:
Views expressed in these public forums are not endorsed by
Drexel University or The Math Forum.


ganesh
Posts:
37
Registered:
2/15/06


help with fzero
Posted:
Aug 3, 2008 7:44 AM


hi i am trying to find roots of a characteristic equation (determinant of matrix). i know the interval within which the root lies. but the characteristic equation also has singularities in that interval. when i try to find out roots of this equation with the function fzero in matlab
>> x=fzero(@fun,0.080)
it returns with an error saying :
>> 'Exiting fzero: aborting search for an interval containing a sign change because complex function value encountered during search. (Function value at 0.0768 is 30.9664+1.77636e015i.) Check function or try again with a different starting value.'
>>
this happens after just two iterations.
i have following questions: 1) why matlab has problem with a complex valued function?
2) Since the function value has not reached zero yet, I still need to search for the root. How do i skip the values where function becomes singular (in this case Complex) ?
any help is greatly appreciated.



