Curve Fitting a Transfer Function

I have a transfer function in the frequency domain and I am looking to curve fit it into a numerator and a denominator for a system. Is there a specific function that I can use to do so if there are both poles and zeros in the transfer function? I have the standard student version toolboxes as well as the system ID toolboxes.

Answer 1

[Sebastian Castro]

In System Identification Toolbox, there is a "tfest" function. Notice that one way to call it is by specifying the data, as well as the number of poles (np) and zeros (nz):

http://www.mathworks.com/help/ident/ref/tfest.html

http://www.mathworks.com/help/ident/ug/how-to-estimate-transfer-function-models-at-the-command-line.html

>> sys = tfest(data,np,nz)

- Sebastian

[Michael Harris]

Thank you Sebastian. I had attempted to use the tfest command previously and the system that I was getting was not even close to a good approximation of my transfer function. The system I was given was just an exponential decay function with no distinct poles or zeros. Do you have any suggestions as to how I can get the tfest command to give me better results?