title: Parameters for using sigmoidal fit in python
body: <p>I used </p>
  
  <pre><code>y = c / (1 + np.exp(-k*(x-x0))) + y0 
  </code></pre>
  
  <p>in python to fit a sigmoid into a curve with points. Can any one tell me what the parmeter "c" means in sigmoidal fit?</p>