pivot for crossfilter

This is a simple pivot function for crossfilter, written as an ES6 module. The lib folder contains ES5 code generated by Babel for UMD module system.

The function returns the counts for a given row and column; and the product of the row/col.

data = [{ product: "A", store: "B"},
{product: "B", store: "A"},
{product: "C", store: "B"}]

fact = crossfilter(data);

pivot( facts, "product", "store")

This code will yield the result:

{
"product": {
"A": 1,
"B": 1,
"C": 1
},
"store": {
"A": 1,
"B": 2
},
"product|store": {
"A|B": 1,
"B|A": 1,
"C|B": 1
}
}