- Did the code crash?
vectfit.m is highly robust so there is a 99.9% probability that you made a mistake. The most common mistake is to specify input arrays with wrong dimensions. See the heading of the vectfit.m for the correct way of doing this.
- Did you get a poor fitting?
If a good fitting exist, Vector Fitting will find it. But not all type of reponses can be fitted with rational functions, so better check your data set. E.g., some (non-physical) responses require unstable poles to be fitted. This situation can be checked on by changing the input parameter "kill" from 2 (enforce stable poles) to 0 (allow stable poles).
If you are unable to figure out out the problem, contact Bjørn Gustavsen