Using a brush to update a donut chart

With much help from Mike and Morgan, here is a D3 donut chart controlled by a custom, one-sided brush.

<!DOCTYPE html>
<meta charset="utf-8">
<head>
  <link href="https://fonts.googleapis.com/css?family=Source+Sans+Pro:300" rel="stylesheet" type="text/css">
<style>
  body, svg {
    font-family: "Source Sans Pro", sans-serif;
    font-weight: 300;
    font-size: 11px;
  }

#selectContainer {
    width: 600px;
    height: 450px;
    position: absolute;
    top:20px;
    left:20px;
  }

.grid-background {
    fill: #fff;
  }

.brush .extent {
    fill:#1874CD;
    fill-opacity: .05;
    shape-rendering: crispEdges;
  }

.count {
    text-anchor:middle;
    fill: #777;
    font-size: 60px;
    position: absolute;
  }

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

//define dimensions
var margin = {top: 15, right: 15, bottom: 15, left: 15},
    width = 400 - margin.left - margin.right,
    height = 400 - margin.top - margin.bottom;
    radius = Math.min(width, height) / 1.8;

// add a percent scale
var x = d3.scale.linear()
    .domain([0, 100])
    .range([0, width]);

// define the brush control
var brush = d3.svg.brush()
    .x(x)
    .extent([0, 10])
    .on("brush", brushend);

// build the svg for the whole thing
var svg = d3.select("body").append("svg")
    .attr("width", width + margin.left + margin.right)
    .attr("height", height + margin.top + margin.bottom)
    .attr('class','brushControl')
  .append("g")
    .attr("transform", "translate(" + margin.left + "," + margin.top + ")");

// tack the brush elements onto the svg
svg.append("rect")
    .attr("class", "grid-background")
    .attr("width", width)
    .attr("height", height);

svg.append("g")
    .attr("class", "x grid")
    .attr("transform", "translate(0," + height + ")");

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

var gBrush = svg.append("g")
    .attr("class", "brush")
    .call(brush);

gBrush.selectAll("rect")
    .attr("height", height);

// set the brush extent to be non-clickable
gBrush.selectAll("rect")
    .style("pointer-events", "none")
    .attr("y", -1)
    .attr("height", height);

// give the right edge of the brush an icon as a handle
gBrush.selectAll(".resize.e")
  .append("image")
    .attr("width", 35)
    .attr("height", 35)
    .attr("y", height/1.1)
    .attr("x", -18)
    .attr("xlink:href", "arrow_right.png");

// add a counter in the middle
d3.selectAll('.brushControl').append('text')
    .attr("x", width/1.8)
    .attr("y", height/1.75)
    .attr('class', 'count')
    .text(Math.round(brush.extent()[1]) + '%');

// choose the pie chart colors
var color = d3.scale.ordinal()
    .range(['#1874CD','#f0f1f1']);

// define the chart type and dimensions
var pie = d3.layout.pie()
    .sort(null);

var arc = d3.svg.arc()
    .innerRadius(radius - 100)
    .outerRadius(radius - 60);

// append the pie chart to the already-defined brush svg
var svg = d3.select(".brushControl").append("svg")
    .attr("width", width + margin.left + margin.right)
    .attr("height", height + margin.top + margin.bottom)
  .append("g")
    .attr("transform", "translate(" + width / 1.85 + "," + height / 1.9 + ")");

// connect the pie chart proportions to the brush extent
var path = svg.selectAll("path")
    .data(pie([brush.extent()[1], 100 - brush.extent()[1]]))
  .enter().append("path")
    .attr("fill", function(d, i) { return color(i); })
    .attr("d", arc);

// update the pie and the counter whenever the brush is moved
function brushend() {
  path.data(pie([brush.extent()[1], 100 - brush.extent()[1]]))
      .attr("d", arc);
  d3.select('text.count')
      .text(Math.round(brush.extent()[1]) + '%');
}

</script>
</body>
</html>

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

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