[GitHub] [incubator-druid] jmarxuach commented on issue #7849: Geometric mean calculation

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jmarxuach commented on issue #7849: Geometric mean calculation
URL: https://github.com/apache/incubator-druid/issues/7849#issuecomment-499936073
 
 
   After some research, I found a solution.
   
   I enabled javascript and i create an aggregator and a post-aggregator .
   
   Agregator SUM_LOG =  ( log(n1)+log(n2)+log(n3)+....) 
   
   ```javascript
   
   {
     "type": "javascript",
     "name": "SUM_LOG",
     "fieldNames": ["column"],
     "fnAggregate" : "function(current, column)      { 
                    if (a>0)  return  current + (Math.log(column)/ Math.log(10)); else return 0;
      }",
     "fnCombine"   : "function(partialA, partialB) { return partialA + partialB; }",
     "fnReset"     : "function()                   { return 0; }"
   }
   ```
   Then I created a post-aggregator : 10^(logSum/count)
   
   ```javascript
   {
     "type": "javascript",
     "name": "GEO_MEAN",
     "fieldNames" : ["SUM_LOG", "count"],
     "function": "function(SUM_LOG, count) { return Math.pow(10, (SUM_LOG/count)); }"
   }
   ```
   
   And that's it !! My feature proposal a sumlog is not needed if you enable javascript. 

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