Function box

src/base/d3.box.js:65–390

(g)

    // For each small multiple…
    function box (g) {
        g.each(function (data, index) {
            data = data.map(value).sort(ascending);
            const _g = select(this);
            const n = data.length;
            let min;
            let max;

            // Leave if there are no items.
            if (n === 0) {return;}

            // Compute quartiles. Must return exactly 3 elements.
            const quartileData = data.quartiles = quartiles(data);

            // Compute whiskers. Must return exactly 2 elements, or null.
            const whiskerIndices = whiskers && whiskers.call(this, data, index),
                whiskerData = whiskerIndices && whiskerIndices.map(_i => data[_i]);

            // Compute outliers. If no whiskers are specified, all data are 'outliers'.
            // We compute the outliers as indices, so that we can join across transitions!
            const outlierIndices = whiskerIndices ?
                range(0, whiskerIndices[0]).concat(range(whiskerIndices[1] + 1, n)) : range(n);

            // Determine the maximum value based on if outliers are shown
            if (showOutliers) {
                min = data[0];
                max = data[n - 1];
            } else {
                min = data[whiskerIndices[0]];
                max = data[whiskerIndices[1]];
            }
            const pointIndices = range(whiskerIndices[0], whiskerIndices[1] + 1);

            // Compute the new x-scale.
            const x1 = scaleLinear()
                .domain(domain && domain.call(this, data, index) || [min, max])
                .range([height, 0]);

            // Retrieve the old x-scale, if this is an update.
            const x0 = this.__chart__ || scaleLinear()
                .domain([0, Infinity])
                .range(x1.range());

            // Stash the new scale.
            this.__chart__ = x1;

            // Note: the box, median, and box tick elements are fixed in number,
            // so we only have to handle enter and update. In contrast, the outliers
            // and other elements are variable, so we need to exit them! Variable
            // elements also fade in and out.

            // Update center line: the vertical line spanning the whiskers.
            const center = _g.selectAll('line.center')
                .data(whiskerData ? [whiskerData] : []);

            center.enter().insert('line', 'rect')
                .attr('class', 'center')
                .attr('x1', width / 2)