var json_from_data = [{acceleration: 15,
cylinders: 4,
displacement: 98,
horsepower: 80,
id: 90,
model_year: 72,
mpg: 28,
name: "dodge colt (sw)",
origin: 1,
weight: 2164},
{acceleration: 14,
cylinders: 8,
displacement: 307,
horsepower: 130,
id: 80,
model_year: 72,
mpg: 13,
name: "chevrolet chevelle concours (sw)",
origin: 1,
weight: 4098}],


    json_from_form = [{color: 'displacement', 
              number: "id",
              x: "cylinders",
              y: "horsepower"}];

$.concat||$.extend({concat:function(b,c){var a=[];
for(x in arguments)a=a.concat(arguments[x]);return a;}});

var new_data = $.concat(json_from_form, json_from_data);

var isDefined = function(v) {return v !== undefined;}
console.log("color --> displacement", new_data.map(function(d) { return d.color}).filter( isDefined) );
console.log("displacement", new_data.map(function(d) { return d.displacement}).filter( isDefined) );