Bucket Script Aggregation - Filter Ratio with STDEV

Hello,
I'm kind of new to ES. I'm searching for the possibilities to do some high level aggregation with ES.

I want to know if I could do this on ES :


                  AVG ( Bucket X ) - AVG ( Bucket  Y) 
              ----------------------------------------------------------
                                   STDEV( Bucket  Y)


I have tried some queries , but the problem is with the division and how can I store the STDEV to apply Ratio filter on.

this is what I did:


GET /index/_search
{
  "size": 0,
  "aggs": {
    "date-ranges": {
      "date_range": {
        "field": "publishDate",
        "format": "yyyy-MM-dd",
        "ranges": [
          {
            "from": "now-61d/d",
            "to": "now-1d/d",
            "key": "count_for_60d"
          }
        ]
      },
      "aggs": {
        "STDEV_60": {
          "extended_stats": {
            "field": "Pol"
          }
        },
        "AVG_Polarity_60": {
          "avg": {
            "field": "Pol"
          }
        }
      }
    },
    "count_for_1d": {
      "filter": {
        "range": {
          "publishDate": {
            "gte": "now-1d/d",
            "lte": "now"
          }
        }
      },
      "aggs": {
        "count_1d": {
          "avg": {
            "field": "Pol"
          }
        }
      }
    }
  }
}

Any tips will be appreciated .. Thanks a lot