Focus+context via brushing with objects d3.js

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Javascript

d3js

I'm new with d3.js. I want to create a timeline with brushing composed by two axes; one for focus and one for context. The problem is that when I add simple element as rectangle o circle on the context axis, I can't see this element in the focus axis during the brushing. Where I wrong?

var elem;
var margin = {top: 10, right: 10, bottom: 100, left: 40},
    margin2 = {top: 10, right: 10, bottom: 20, left: 40},
    width = 960 - margin.left - margin.right,
    height = 150 - margin.top - margin.bottom,
    height2 = 150 - margin2.top - margin2.bottom;

var parseDate = d3.time.format("%b %Y").parse;

var x = d3.time.scale().range([0, width]),
    x2 = d3.time.scale().range([0, width]);


var xAxis = d3.svg.axis().scale(x).orient("bottom"),
    xAxis2 = d3.svg.axis().scale(x2).orient("bottom");


var brush = d3.svg.brush()
    .x(x2)
    .on("brush", brushed);

var area = d3.svg.area()

    .x(function(d) { return x(d.date); })


var area2 = d3.svg.area()

    .x(function(d) { return x2(d.date); })


var svg = d3.select("#timeline").append("svg")
    .attr("width", width + margin.left + margin.right)
    .attr("height", height + margin.top + margin.bottom);

svg.append("defs").append("clipPath")
    .attr("id", "clip")
  .append("rect")
    .attr("width", width)
    .attr("height", height);

var focus = svg.append("g")
    .attr("class", "focus")
    .attr("transform", "translate(" + margin.left + "," + margin.top + ")");

var context = svg.append("g")
    .attr("class", "context")
    .attr("transform", "translate(" + margin2.left + "," + margin2.top + ")");

d3.csv("Timeline-portlet/sp500.csv", type, function(error, data) {
  x.domain(d3.extent(data.map(function(d) { return d.date; })));

  x2.domain(x.domain());


  focus.append("path")
      .datum(data)
      .attr("class", "area")
      .attr("d", area);

  focus.append("g")
      .attr("class", "x axis")
      .attr("transform", "translate(0," + height + ")")
      .call(xAxis);


  context.append("path")
      .datum(data)
      .attr("class", "area")
      .attr("d", area2);

  context.append("g")
      .attr("class", "x axis")
      .attr("transform", "translate(0," + height2 + ")")
      .call(xAxis2);

  context.append("g")
      .attr("class", "x brush")
      .call(brush)
     .selectAll("rect")
      .attr("y", -6)
      .attr("height", height2 + 7) ;

  var a=new Date('2009-03-10');
  var b=new Date('2009-05-10');

  var dateTIM=[a,b];



  elem= svg.append("g").attr("transform", "translate(0," + 140 + ")").selectAll(".objTim").data(dateTIM).enter().append("rect").attr("class","objTim")
  .attr("d",elem ).attr("x", function(d){return x2(d)-5}).attr("width", 10)
  .attr("y", -25).attr("height",30).attr("fill","#00C")


});

function brushed() {
  x.domain(brush.empty() ? x2.domain() : brush.extent());
  focus.select(".objTim").attr("d",elem);
  focus.select(".area").attr("d", area);
  focus.select(".x.axis").call(xAxis);
}

function type(d) {
  d.date = parseDate(d.date);
  d.price = +d.price;
  return d;
} 

Regards

What I have tried:

I want to create a timeline with brushing composed by two axes; one for focus and one for context.