title: How can I find equation of a plot connecting data points in Matlab?
body: <p>I have various plots (with <code>hold on</code>) as show in the following figure:
  <img src="https://i.stack.imgur.com/qgsor.jpg" alt="enter image description here"></p>
  
  <p>I would like to know how to find equations of these six curves in Matlab. Thanks.</p>