dataWidthPortion (percentage) {
        if (!arguments.length) {
            return this._dataWidthPortion;
        }
        this._dataWidthPortion = percentage;
        return this;
    }
Get or set the portion of the width of the box to show data points.
@example
// If individual data points are rendered increase the data box.
chart.dataWidthPortion(0.9);
@param {Number} [percentage=0.8]
@returns {Number|BoxPlot}