gistfile1.js

function (key, values, rereduce) {
        // value -> [count, min, max, mean]
        var i = 0
          , l = values.length
          , min = values[i][2] // set min to the first max
          , max = 0
          , mean = 0
          , count = 0
          ;
        
        for (; i < l; i++) {
          count = count + values[i][0];
          min = Math.min(min, values[i][1]);
          max = Math.max(max, values[i][2]);
          mean = ((mean * count) + (values[i][3] * values[i][0])) / (count);
        }
        
        return [count, min, max, mean];
    }