xp(1i*phase) * exp(time * (1i*2*pi*freq - damp) )
</p>
<p>
The function requires 2-4 input parameters: the <code>spectrum</code> to be fit and 
its corresponding <code>time</code> vector are necessary; the <code>method</code> and <code>order</code> if not 
provided will revert to the defaults. 
</p>
<p>
The third input determines the <code>method</code> used to fit the model to the spectrum, the three possible inputs include:
</p>
<ul>
<li><code>'kt'</code>: Kumaresan and Tufts linear prediction and singula