Focus+Context via Brushing

This examples demonstrates how to use D3's brush component to implement focus + context zooming. Click and drag in the small chart below to pan or zoom.

forked from mbostock's block: Focus+Context via Brushing

<!DOCTYPE html>
<meta charset="utf-8">
<style>

svg {
  font: 10px sans-serif;
}

.area {
  fill: #B4B4B4;
  opacity: .8;
  clip-path: url(#clip);
}

.axis path,
.axis line {
  fill: none;
  stroke: #000;
  shape-rendering: crispEdges;
}

.brush .extent {
  stroke: black;
  fill: white;
  fill-opacity: .6;
  shape-rendering: crispEdges;
}

</style>
<body>
<script src="//d3js.org/d3.v3.min.js"></script>
<script>

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 parseDate = d3.time.format("%Y").parse;
//%b 
  
  
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", brushed);

var area = d3.svg.area()
    .interpolate("monotone")
    .x(function(d) { return x(d.date); })
    .y0(height)
    .y1(function(d) { return y(d.caseid); });

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("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("totaltopics.csv", type, function(error, data) {
  console.log(data);
  x.domain(d3.extent(data.map(function(d) { return d.date; })));
  y.domain([0, d3.max(data.map(function(d) { return d.caseid; }))]);
  x2.domain(x.domain());
  y2.domain(y.domain());

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

focus.append("g")
      .attr("class", "y axis")
      .call(yAxis);

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);
});

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

function type(d) {
  d.date = parseDate(d.date);
  //d.date = +d.date;
  d.caseid = +d.caseId;
  return d;
}

</script>

https://d3js.org/d3.v3.min.js