I was doing some syntax error. We can simply resolve this
<ul>
<li ng-click="expression= 'created_at'" ng-class= "latest_icon : expression == 'created_at'">Latest </li>
<li ng-click="expression= 'popularity'" ng-class= "popular_icon : expression == 'popularity'">Latest </li>
</ul>
Here latest_icon and popular_icon are classes name which activate according to selected list.