It would be nice if there was an extra finalizer option on the group command. Right now it is difficult to implement an average function using just group(). While this could be done in the calling language, in some cases it is nice to be able to do everything in one place in javascript.

Example

db.coll.group(
{key:"date"
,initial:

{ct:0, sum:0}

,reduce: function(doc, out)

{out.ct++; out.sum += doc.val}

,final: function(result)

{result.sum = result.ct ? result.sum/result.ct : 0}

})

Ideally, if the final function returned a non-undefined result it would replace that position in the output, similar to a map function.