<table ng-table="tableParams" show-filter="true" class="table" >
    <tr  ng-class="{'danger': project.rag <= 35,'warning': project.rag > 35 && project.rag < 70,'success': project.rag > 70}" ng-repeat="project in $data">
        <td data-title="'PRN'" sortable="'prn'" filter="{'prn': 'text'}">
            {{project.prn}}
        </td>
    </tr>
</table>

因此,当用户将鼠标悬停在这些< td>上时我想从控制器显示一个值.我该怎么做呢？做这个的最好方式是什么？