reductio/src/cap.js

Reductio: Crossfilter groupings

var pluck = function(n){
    return function(d){
        return d[n];
    };
};

// supported operators are sum, avg, and count
const _grouper = function(path, prior){
    if(!path) path = function(d){return d;};
    return function(p, v){
        if(prior) prior(p, v);
        var x = path(p), y = path(v);
        if(typeof y.count !== 'undefined') x.count += y.count;
        if(typeof y.sum !== 'undefined') x.sum += y.sum;
        if(typeof y.avg !== 'undefined') x.avg = x.sum/x.count;
        return p;
    };
};

const cap = function (prior, f, p) {
    var obj = f.reduceInitial();
    // we want to support values so we'll need to know what those are
    var values = p.values ? Object.keys(p.values) : [];
    var _othersGrouper = _grouper();
    if (values.length) {
        for (var i = 0; i < values.length; ++i) {
            _othersGrouper = _grouper(pluck(values[i]), _othersGrouper);
        }
    }
    return function (cap, othersName) {
        if (!arguments.length) return prior();
        if( cap === Infinity || !cap ) return prior();
        var all = prior();
        var slice_idx = cap-1;
        if(all.length <= cap) return all;
        var data = all.slice(0, slice_idx);
        var others = {key: othersName || 'Others'};
        others.value = f.reduceInitial();
        for (var i = slice_idx; i < all.length; ++i) {
            _othersGrouper(others.value, all[i].value);
        }
        data.push(others);
        return data;
    };
};

export default cap;