title: How to toggle Angular material expansion panel programmatically
body: <p>I just started working on an Angular 4 project with material design.</p>
  <p>I am currently working with the expansion component, <a href="https://material.angular.io/components/expansion/overview" rel="noreferrer">the API states</a> that  <em>a disabled expansion panel can't be toggled by the user, but can still be manipulated programmatically</em>. I don't know however, how you can toggle your panel programmatically.</p>
  <p>What is the preferred way in Angular to simulate this?</p>