median, mean, standard deviation underscore mixins

stats.js

_.mixin({
	median : function(data) {
		if(data.length < 1) return 0;
    		var slot = (data.length+1) / 2;
		if (slot % 1 === 0) {
			return data[slot-1];
		} else {
			var lower = Math.floor(slot);
			var upper = Math.ceil(slot);
			return (data[lower-1] + data[lower-1]) / 2;
		}
	},
	mean: function(data) {
		if (data.length < 1) return 0;
		return _.reduce(data, function(memo, num) { return memo + num; }, 0)/data.length;
	},
	stdev: function(data) {
		if (data.length < 1) return 0;
		var setMean = _.mean(data);
		var totalDeviation = _.reduce(data, function(memo, num){ return memo + Math.pow(setMean - num, 2);  },0);
		return Math.sqrt(totalDeviation/data.length);
	}
});

return (data[lower-1] + data[lowerupper-1]) / 2;