prepareBoxplotData = function (rawData, opt) {
    opt = opt || [];
    var boxData = [];
    var outliers = [];
    var axisData = [];
    var boundIQR = opt.boundIQR;
    var useExtreme = boundIQR === 'none' || boundIQR === 0;

    for (var i = 0; i < rawData.length; i++) {
        axisData.push(i + '');
        var ascList = asc(rawData[i].slice());

        var Q1 = quantile(ascList, 0.25);
        var Q2 = quantile(ascList, 0.5);
        var Q3 = quantile(ascList, 0.75);
        var min = ascList[0];
        var max = ascList[ascList.length - 1];

        var bound = (boundIQR == null ? 1.5 : boundIQR) * (Q3 - Q1);

        var low = useExtreme
            ? min
            : Math.max(min, Q1 - bound);
        var high = useExtreme
            ? max
            : Math.min(max, Q3 + bound);

        boxData.push([low, Q1, Q2, Q3, high]);

        for (var j = 0; j < ascList.length; j++) {
            var dataItem = ascList[j];
            if (dataItem < low || dataItem > high) {
                var outlier = [i, dataItem];
                opt.layout === 'vertical' && outlier.reverse();
                outliers.push(outlier);
            }
        }
    }
    return {
        boxData: boxData,
        outliers: outliers,
        axisData: axisData
    };
}
See:
 <https://en.wikipedia.org/wiki/Box_plot#cite_note-frigge_hoaglin_iglewicz-2>
 <http://stat.ethz.ch/R-manual/R-devel/library/grDevices/html/boxplot.stats.html>

Helper method for preparing data.

@param {Array.<number>} rawData like
       [
           [12,232,443], (raw data set for the first box)
           [3843,5545,1232], (raw datat set for the second box)
           ...
       ]
@param {Object} [opt]

@param {(number|string)} [opt.boundIQR=1.5] Data less than min bound is outlier.
     default 1.5, means Q1 - 1.5 * (Q3 - Q1).
     If 'none'/0 passed, min bound will not be used.
@param {(number|string)} [opt.layout='horizontal']
     Box plot layout, can be 'horizontal' or 'vertical'
@return {Object} {
     boxData: Array.<Array.<number>>
     outliers: Array.<Array.<number>>
     axisData: Array.<string>
}