More fun with CouchDB, this time taking an average of something:

```
// map
function(doc){
emit(null, doc.info.size) // in place of doc.info.size, you'd put whatever
// value you want averaged here
}
// reduce
function(keys, values, rereduce) {
if (!rereduce){
var length = values.length
return [sum(values) / length, length]
}else{
var length = sum(values.map(function(v){return v[1]}))
var avg = sum(values.map(function(v){
return v[0] * (v[1] / length)
}))
return [avg, length]
}
}
```

The end result will be 2 values, the first is the average, the second is the total number of values that we took an average of. Phew! Who woulda thought taking an average would be so *involved!*