title: How to obtain damping ratio with Curve Fitting Toolbox
body: <p>I have some experimental data from an oscillating system (time domaine) and I would like to get an approximation of the damping ratio (zeta). I have already try to use the half-power band width method with the vibrationdata Matlab package. But I would like to compare the result with another method.</p>
  
  <p>I found several methods in this paper : <a href="http://www.vce.at/sites/default/files/uploads/downloads/2007_damping_estimation.pdf" rel="nofollow">www.vce.at/sites/default/files/uploads/downloads/2007_damping_estimation.pdf</a> and I would like to try to do the curve fitting method with the Curve Fitting Toolbox of Matlab (R2014b) (chapter 2.2.2 Curve fitting in the paper).</p>
  
  <p>It's the first time I use this Toolbox with a custom equation, so, I do not really know how to do it with my sample data.</p>
  
  <p>I do not know how to write in the Curve Fitting Toolbow, the equation of the paper as it involves differentiate equation...</p>
  
  <p>Can anyone help me regarding this.</p>