Function getAggregateFunction

src/transforms/aggregate.js:272–438

(opts, conversions)

}

function getAggregateFunction(opts, conversions) {
    var func = opts.func;
    var d2c = conversions.d2c;
    var c2d = conversions.c2d;

    switch(func) {
        // count, first, and last don't depend on anything about the data
        // point back to pure functions for performance
        case 'count':
            return count;
        case 'first':
            return first;
        case 'last':
            return last;

        case 'sum':
            // This will produce output in all cases even though it's nonsensical
            // for date or category data.
            return function(array, indices) {
                var total = 0;
                for(var i = 0; i < indices.length; i++) {
                    var vi = d2c(array[indices[i]]);
                    if(vi !== BADNUM) total += vi;
                }
                return c2d(total);
            };

        case 'avg':
            // Generally meaningless for category data but it still does something.
            return function(array, indices) {
                var total = 0;
                var cnt = 0;
                for(var i = 0; i < indices.length; i++) {
                    var vi = d2c(array[indices[i]]);
                    if(vi !== BADNUM) {
                        total += vi;
                        cnt++;
                    }
                }
                return cnt ? c2d(total / cnt) : BADNUM;
            };

        case 'min':
            return function(array, indices) {
                var out = Infinity;
                for(var i = 0; i < indices.length; i++) {
                    var vi = d2c(array[indices[i]]);
                    if(vi !== BADNUM) out = Math.min(out, vi);
                }
                return (out === Infinity) ? BADNUM : c2d(out);
            };

        case 'max':
            return function(array, indices) {
                var out = -Infinity;
                for(var i = 0; i < indices.length; i++) {
                    var vi = d2c(array[indices[i]]);
                    if(vi !== BADNUM) out = Math.max(out, vi);