未捕获的ReferenceError：$未定义django graphos

Question

<script type="text/javascript">
 $(function () {
  $.plot(
    $("#line_chart"), 
    [{"data": [[2005, 205], [2015, 210], [2015, 12], [2014, 122], [2015, 12], [2015, 2]], "label": "PlacedStudent"}], 
    {"series": {"lines": {"show": "true"}}, "legend": {"position": "ne"}, "xaxis": {"mode": "categories"}, "title": "PlaceMentReport"}
  );
 });
</script>

这里有什么不对，我正在

  

未捕获的ReferenceError：$未定义