Incremental stats

incr.js

var stats = {
    q:     0,
    count: 0,
    min:   Infinity,
    max:   -Infinity,
    sum:   0,
    mean:  0
};

var variance = stats.q / stats.count;
var standard_deviation = Math.sqrt(variance);

function push (value) {
    if (isNaN(value)) {
        throw 'Cannot handle NaN.';
    }
    stats.count++;
    stats.min = Math.min(stats.min, value);
    stats.max = Math.max(stats.max, value);
    stats.sum += value;
    var previous_mean = stats.mean;
    stats.mean = stats.mean + (value - stats.mean) / stats.count;
    stats.q = stats.q + (value - previous_mean) * (value - stats.mean);
};