title: Invalid Scope Parameter in RunningValue in a line chart
body: <p>I can't for the life of me figure this out.  I have a table in SSRS that has a data that looks like this:</p>
  
  <pre><code>days   P  
  0      0.99  
  26     0.98  
  57     1  
  97     0.97  
  99     0.99  
  </code></pre>
  
  <p>What I want to do is plot a running product of the values in P. I can get them in a table by calculating the following value:</p>
  
  <pre class="lang-vb prettyprint-override"><code>=exp(RunningValue(Fields!P.Value, Sum, "data"))
  </code></pre>
  
  <p>And that works fine.  When I try to scatter-plot it, however, nothing is showing up in my plots.</p>
  
  <p>For my value I have:</p>
  
  <pre><code>X: =Fields!d.Value  
  Y: =exp(RunningValue(Fields!P.Value, Sum, "data"))
  </code></pre>
  
  <p>Any Category or Series value I try seems to break the plot, giving me some variation on the following error:</p>
  
  <blockquote>
    <p>The DataPoint expression for the chart 'chart1' has a scope parameter that is not valid for RunningValue, RowNumber or Previous. The scope parameter must be set to a string constant that is equal to the name of a containing group within the matrix 'chart1'.</p>
  </blockquote>