无法更新流程栏

Question

我的行为与http://responsiweb.com/themes/preview/ace/1.3.3/elements.html完全相同 这是html代码：

    <div class="col-xs-4">
        <div class="easy-pie-chart percentage" data-percent="0" data-color="#D15B47">
            <span class="percent">0</span>%
        </div>
        <hr />
        <div class="easy-pie-chart percentage" data-percent="0" data-color="#87CEEB">
            <span class="percent">0</span>%
        </div>
        <hr />
        <div class="easy-pie-chart percentage" data-percent="60" data-color="#87B87F">
            <span class="percent">60</span>%
        </div>
    </div>
    <!-- /.col -->
    <button id="incre_know_one">
        Increase processwheel</button>

和javascript：

  $("#incre_know_one").click(function () {
        $(".easy-pie-chart").attr('data-percent', '50');
        $('.easy-pie-chart span').html('50');
    });

它更新文本但不填充颜色..任何建议???