Method stack

src/base/stack-mixin.js:103–122

* Stack a new crossfilter group onto this chart with an optional custom value accessor. All stacks * in the same chart will share the same key accessor and therefore the same set of keys. * * For example, in a stacked bar chart, the bars of each stack will be positioned using the same

(group, name, accessor)

     * @returns {Array<{group: crossfilter.group, name: String, accessor: Function}>|StackMixin}
     */
    stack (group, name, accessor) {
        if (!arguments.length) {
            return this._stack;
        }

        if (arguments.length <= 2) {
            accessor = name;
        }

        const layer = {group: group};
        if (typeof name === 'string') {
            layer.name = name;
        }
        if (typeof accessor === 'function') {
            layer.accessor = accessor;
        }
        this._stack.push(layer);

        return this;
    }

    group (g, n, f) {
        if (!arguments.length) {