<!DOCTYPE html>
<html>

<head>
  <script data-require="angular.js@1.4.8" data-semver="1.4.8" src="https://cdnjs.cloudflare.com/ajax/libs/angular.js/1.4.8/angular.min.js"></script>
</head>

<body ng-app>
  <div ng-init="radioButton = 'Happy'">
      <input type="radio" value="Happy" ng-model="radioButton"/> Happy
      <input type="radio" value="Angry" ng-model="radioButton"/> Angry
      <input type="radio" value="Sad" ng-model="radioButton"/> Sad
      You are "<span ng-bind="radioButton"></span>", not?. Please Select!
  </div>
</body>

</html>
http://blog.allii.ir/2016/01/angularjs-begineer-intermediate-course-basics-part-one/#scopes