Freedman-Diaconis thumb rule for number of bins of a histogram

bucket_sizes.js

// metric = array of real numbers (like > 100 or something)
// IQR = inter-quaartile-range
function numBins(metric, defaultBins) {
    var h = binWidth(metric), ulim = Math.max.apply(Math, metric), llim = Math.min.apply(Math, metric);
    if (h <= (ulim - llim) / metric.length) {
        return defaultBins || 10; // Fix num bins if binWidth yields too small a value.
    }
    return Math.ceil((ulim - llim) / h);
}

function binWidth(metric) {
    return 2 * iqr(metric) * Math.pow(metric.length, -1/3);
}

function iqr(metric) {
    var sorted = metric.slice(0).sort(function (a, b) { return a - b; });
    var q1 = sorted[Math.floor(sorted.length / 4)];
    var q3 = sorted[Math.floor(sorted.length * 3 / 4)];
    return q3-q1;
}

var metric = []

for(var i=0; i<1866; i++){
    metric.push(i);
}

console.log(numBins(metric, 10));