Brushing Bar Chart

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. With the abitility to zoom and pan in the Focus view using d3.zoom behavior.

forked from sbreslav's block: Focus+Context via Brushing & Zoom & Pan

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

svg {
  font: 10px sans-serif;
}

.bar {
  fill: steelblue;
  clip-path: url(#clip);
}
  
.subBar { 
  fill: gray;
  opacity: 0.5;
}

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

.brush .extent {
  stroke: #fff;
  fill: steelblue;
  fill-opacity: .25;
  shape-rendering: crispEdges;
}

</style>
<body>
<script src="https://d3js.org/d3.v3.min.js"></script>
<script>
  
var data = [];

for (var i = 0; i < 300; i++) {
  var datum = {};
  datum.date = i;
  datum.price = Math.floor(Math.random() * 600);
  data.push(datum);
}  
  
var margin = {top: 10, right: 10, bottom: 100, left: 40},
    margin2 = {top: 430, right: 10, bottom: 20, left: 40},
    width = 750 - margin.left - margin.right,
    height = 500 - margin.top - margin.bottom,
    height2 = 500 - margin2.top - margin2.bottom;

var x = d3.scale.ordinal().rangeBands([0, width], .1),
    x2 = d3.scale.ordinal().rangeBands([0, width], .1),
    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").tickValues([]),
    yAxis = d3.svg.axis().scale(y).orient("left");

x.domain(data.map(function(d){ return d.date}));
	  y.domain([0, d3.max(data, function(d) { return d.price;})]);
  	x2.domain(x.domain());
	  y2.domain(y.domain());
		
  var brush = d3.svg.brush()
							  .x(x2) 
							  .on("brush", brushed);

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

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 + ")");

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

focus.append("g")
      .attr("class", "y axis")
      .call(yAxis);
	 
  console.log(x(data[0].date))
 	enter(data)
  updateScale(data)
  
  var subBars = context.selectAll('.subBar')
                                  	.data(data)
	
  subBars.enter().append("rect")
		  .classed('subBar', true)
			.attr(
    	{
        height: function (d)
        {
          return height2 - y2(d.price);
        },
        width: function(d){ return x.rangeBand()},
        x: function(d) {

return x2(d.date);
        },
        y: function(d)
        {
          return y2(d.price)
        }
      })

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 updatedData = data.slice(start, end);

update(updatedData);
    enter(updatedData);
    exit(updatedData);
  	updateScale(updatedData)

}
 
  function updateScale(data)
  { 
    		var tickScale = d3.scale.pow().range([data.length / 10, 0]).domain([data.length, 0]).exponent(.5)

var brushValue = brush.extent()[1] - brush.extent()[0];
    if(brushValue === 0){
      brushValue = width;
    }

var tickValueMultiplier = Math.ceil(Math.abs(tickScale(brushValue)));  
  	var filteredTickValues = data.filter(function(d, i){return i % tickValueMultiplier === 0}).map(function(d){ return d.date})

focus.select(".x.axis").call(xAxis.tickValues(filteredTickValues));
    focus.select(".y.axis").call(yAxis);
  }
  
  function update(data)
  {
		  x.domain(data.map(function(d){ return d.date}));
		  y.domain([0, d3.max(data, function(d) { return d.price;})]);

var bars =  focus.selectAll('.bar')
          .data(data)
      bars
        .attr(
        {  
          height: function (d, i)
          { 
            return height - y(d.price);
          },
          width: function(d){ 
            return x.rangeBand()
          },
          x: function(d) {

return x(d.date);
          },
          y: function(d)
          {
            return y(d.price)
          }
        })

} 
  
  function exit(data)
  {
		var bars =  focus.selectAll('.bar').data(data)
		bars.exit().remove()
  }
  
  function enter(data)
  {
    	x.domain(data.map(function(d){ return d.date}));
		  y.domain([0, d3.max(data, function(d) { return d.price;})]);

var bars =  focus.selectAll('.bar')
          .data(data)
      bars.enter().append("rect")
        .classed('bar', true)
        .attr(
        {  
          height: function (d, i)
          { 
            return height - y(d.price);
          },
          width: function(d){ 
            return x.rangeBand()
          },
          x: function(d) {
 
            return x(d.date);
          },
          y: function(d)
          {
            return y(d.price)
          }
        })
  }

</script>

Modified http://d3js.org/d3.v3.min.js to a secure url

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