Context和Brush Scatterplot d3.js

Question

跟进已回答的问题

Moving Scatter Plot Circles With Context Zooming And Brush In D3

var margin = {top: 10, right: 10, bottom: 100, left: 40},
    margin2 = {top: 430, right: 10, bottom: 20, left: 40},
    width = 960 - margin.left - margin.right,
    height = 500 - margin.top - margin.bottom,
    height2 = 500 - margin2.top - margin2.bottom;
var data = [{
    'Wed Jan 23 00:00:00 IST 2013': 3383387
}, {
    'Thu Jan 24 00:00:00 IST 2013': 3883387
}, {
    'Fri Jan 25 00:00:00 IST 2013': 4383387
}, {
    'Sat Jan 26 00:00:00 IST 2013': 2383387
}, {
    'Sun Jan 27 00:00:00 IST 2013': 5383387
}, {
    'Mon Jan 28 00:00:00 IST 2013': 2283387
}];
var format = d3.time.format("%a %b %d %H:%M:%S IST %Y");
var parseDate = d3.time.format("%b %Y").parse;
var x = d3.time.scale().range([0, width]),
    x2 = d3.time.scale().range([0, width]),
    y = d3.scale.linear().range([height, 0]),
    y2 = d3.scale.linear().range([height2, 0]);
var xAxis = d3.svg.axis().scale(x).orient("bottom"),
    xAxis2 = d3.svg.axis().scale(x2).orient("bottom"),
    yAxis = d3.svg.axis().scale(y).orient("left");
var brush = d3.svg.brush()
    .x(x2)
    .on("brush", brush);
var area = d3.svg.area()
    .interpolate("monotone")
    .x(function(d) { return x(format.parse(d3.keys(d)[0])); })
    .y0(height)
    .y1(function(d) { return y(d3.values(d)[0]); });
var area2 = d3.svg.area()
    .interpolate("monotone")
    .x(function(d) { return x2(format.parse(d3.keys(d)[0])); })
    .y0(height2)
    .y1(function(d) { return y2(d3.values(d)[0]); });
var svg = d3.select("body").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("transform", "translate(" + margin.left + "," + margin.top + ")");
var context = svg.append("g")
    .attr("transform", "translate(" + margin2.left + "," + margin2.top + ")");
  x.domain(d3.extent(data.map(function(d) { return format.parse(d3.keys(d)[0]); })));
  y.domain([0, d3.max(data.map(function(d) { return d3.values(d)[0]; }))]);
  x2.domain(x.domain());
  y2.domain(y.domain());
  focus.append("path")
      .datum(data)
      .attr("clip-path", "url(#clip)")
      .attr("d", area);
  focus.append("g")
      .attr("class", "x axis")
      .attr("transform", "translate(0," + height + ")")
      .call(xAxis);
  focus.append("g")
      .attr("class", "y axis")
      .call(yAxis);
  context.append("path")
      .datum(data)
      .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 circlegroup = focus.append("g");
    circlegroup.attr("clip-path", "url(#clip)");
    circlegroup.selectAll('.dot')
    .data(data)
    .enter().append("circle")
    .attr('class', 'dot')
    .attr("cx",function(d){ return x(format.parse(d3.keys(d)[0]));})
    .attr("cy", function(d){ return y(d3.values(d)[0]);})
    .attr("r", function(d){ return 4;})
    .on('mouseover', function(d){ d3.select(this).attr('r', 8)})
    .on('mouseout', function(d){ d3.select(this).attr('r', 4)});    

function brush() {
  x.domain(brush.empty() ? x2.domain() : brush.extent());
  focus.select("path").attr("d", area);
  focus.select(".x.axis").call(xAxis);
  circlegroup.selectAll(".dot").attr("cx",function(d){ return x(format.parse(d3.keys(d)[0]));}).attr("cy", function(d){ return y(d3.values(d)[0]);});
}

http://jsfiddle.net/PyvZ7/7/

如何将下图更改为散点图而不是区域图。

请帮助。