Average of counts on sub-buckets

Hello, I am using the latest stable version of Kibana and was wondering if there was a way to get the average of the count. Im not sure if its possible or not but when selecting average i can only select a numeric field and not the counts of another aggregation.

So if i have a line chart of login count per user (over a monthly date histo), how can i show another line with the average of those users logins. Thanks

From the looks of it i believe this is not supported and the only thing i could see would be creating another index that contains the count for each user per day, then i can use the normal average on the count field.