how to continue program with fzero error

Hi,

I am using fzero to solve a nonlinear univariate function. However, I am iterating over many parameter values. So, if fzero can't find a root for one set of parameters, that is fine, but I want it to continue to the next set. However, I keep getting the error

??? Error using ==> fzero at 293 The function values at the interval endpoints must differ in sign.

Can anyone tell me the proper way to handle this? Should I go into the function, comment out the error and put a default output, or is there a better way to do this. Thanks.

All the best, Bob

Answer 1

[Matt Fig]

Use a TRY-CATCH block. I'll assume you are looping over the parameter set and storing the roots in a variable S.

cnt = 1;
for ii = PARAMS
  try
      T = fzero(...);
      cnt = cnt + 1;
      S(cnt) = T;  % If FZERO errors, this assignment won't happen.
  catch
      fprintf('No root found for parameter %f\n',ii); %optioinal
  end
end

[Jan]

Voted: Catching an error is more general than avoiding it.

[Bob Johnson]

Great! This is what I was looking for. Thanks a lot.

Answer 2

[Walter Roberson]

Try-catch will certainly work, but I wonder why you don't just do the two endpoint evaluations yourself and skip the fzero call if the signs are the same?

[Jan]

Voted. Avoiding an error is superior to catching it.

[Bob Johnson]

True. Thanks. I will do this as well. Much appreciated