title: Ag Grid aggregation function with Valuegetter
body: <p>In AgGrid, I am tyring to use aggregation functions and valuegetter on the same column. It seems that because of valuegetter, my aggreation functions are not working, I just get 0 or null value on aggregation. Could you please check my code for any possible solutions?
  Thanks.</p>
  
  <pre><code>{ headerName: "Price", filter: "agNumberColumnFilter", valueGetter: priceValueGetter, allowedAggFuncs: ['avg', 'sum', 'min', 'max']};
  
  
  function priceValueGetter(params) {
      var value = '';
  
      if (params.data) {
          var EPrice = params.data.a;
          var p1 = params.data.b;
          if (EPrice &amp;&amp; p1) {
              value = (EPrice - p1).toFixed(2);
          }
      }
      return value;
  }
  </code></pre>