var map = function() {
    var key = {
        year: this.date.getFullYear(), 
        //month: this.date.getMonth(), 
        day: this.date.getDate()
    };
    
    key['domain'] = this.domain;
    key['stat'] = "yandexCitation";
    emit(key, this.stats.yandexCitation);
    
    key['domain'] = this.domain;
    key['stat'] = "pageRank";
    emit(key, this.stats.pageRank);
    
    key['domain'] = this.domain;
    key['stat'] = "yandexIndex";
    emit(key, this.stats.yandexIndex);
    
    key['domain'] = this.domain;
    key['stat'] = "googleIndex";
    emit(key, this.stats.googleIndex);
};

var reduce = function(key, values) {
    function median(values) {
        values.sort( function(a,b) {return a - b;} );
        var half = Math.floor(values.length/2);
        if(values.length % 2)
            return values[half];
        else
            return (values[half-1] + values[half]) / 2.0;
    }
    return median(values);
};

db.SitesHistory.mapReduce(map, reduce, {
    out: { inline: 1 }
});