title: Validate Radio Button AngularJS
body: <p>This seems like it should be fairly easy, but I'm not finding the answer.  I have a form where I need to validate that a selection has been made from a radio group.  I tried using the 'required' attribute on the radio buttons, but when the form is validated it complains unless all the radio buttons are selected (which is impossible by design).  </p>
  
  <p>What is the proper way to validate a radio group selection in AngularJS?</p>
  
  <pre><code>&lt;form name="myForm" ng-submit="submitForm()" ng-controller="ExampleController"&gt;
    &lt;input type="radio" ng-model="color" value="red" required&gt;  Red &lt;br/&gt;
    &lt;input type="radio" ng-model="color" value="green" required&gt; Green &lt;br/&gt;
    &lt;input type="radio" ng-model="color" value="blue" required&gt; Blue &lt;br/&gt;
    &lt;tt&gt;color = {{color | json}}&lt;/tt&gt;&lt;br/&gt;
    &lt;button type="submit"&gt;Submit&lt;/button&gt;
  &lt;/form&gt;
  </code></pre>
  
  <p>Clicking the submit button in the Plnkr shows the behavior.</p>
  
  <p><a href="http://plnkr.co/edit/3qcIbMvJk19OvokcHe2N?p=preview">http://plnkr.co/edit/3qcIbMvJk19OvokcHe2N?p=preview</a></p>