Need Help in D3 Sankey Chart

Question

I had a requirement in which the user will click within sankey chart area and drag the mouse across different nodes of Sankey Chart and all the Nodes which comes under selected area should show their names below in another div tag .

Any ideas how it can be achieved ?

This Link might Help : How to make nodes in sankey diagram clickable using d3.js library

var node = svg.append("g").selectAll(".node")
      .data(graph.nodes)
    .enter().append("g")
      .attr("class", "node")
      .attr("transform", function(d) { 
          return "translate(" + d.x + "," + d.y + ")"; })
    .on("click",function(d){
        if (d3.event.defaultPrevented) return;
        alert("clicked!"+d.value);
    })
    .call(d3.behavior.drag()
      .origin(function(d) { return d; })
      .on("dragstart", function() { 
          this.parentNode.appendChild(this); })
      .on("drag", dragmove));

My code so far:

I just want to to capture all the node name on which the mouse is dragged (mouse click down -> drag across sankey chart to define area -> mouse click up):

var margin = {top: 1, right: 1, bottom: 6, left: 1},
    width = 960 - margin.left - margin.right,
    height = 500 - margin.top - margin.bottom;

var formatNumber = d3.format(",.0f"),   //decimal places
    format = function(d) { return formatNumber(d) + " TWh"; },
    color = d3.scale.category20();

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

var sankey = d3.sankey()
    .nodeWidth(15)
    .nodePadding(10)
    .size([width, height]);

var path = sankey.link();

//d3.json("energy.json", function(energy) {


d3.json("numbers-subset.json", function(energy) {



  sankey
      .nodes(energy.nodes)
      .links(energy.links)
      .layout(32);

  var link = svg.append("g").selectAll(".link")
      .data(energy.links)
    .enter().append("path")
      .attr("class", "link")
      .attr("d", path)
      .style("stroke-width", function(d) { return Math.max(1, d.dy); })
      .sort(function(a, b) { return b.dy - a.dy; });


  link.append("title")
      .text(function(d) { return d.source.name + " → " + d.target.name + "\n" + format(d.value); });


  var node = svg.append("g").selectAll(".node")
      .data(energy.nodes)
    .enter().append("g")
      .attr("class", "node")
      .attr("transform", function(d) { return "translate(" + d.x + "," + d.y + ")"; })
    .call(d3.behavior.drag()
      .origin(function(d) { return d; })
      .on("dragstart", function() { this.parentNode.appendChild(this); })
      .on("drag", dragmove));

  node.append("rect")
      .attr("height", function(d) { return d.dy; })
      .attr("width", sankey.nodeWidth())
      .style("fill", function(d) { return d.color = color(d.name.split("|")[0]); })
      .style("stroke", function(d) { return d3.rgb(d.color).darker(2); })
    .append("title")
      .text(function(d) { return d.name + "\n" + format(d.value); });

  node.append("text")
      .attr("x", -6)
      .attr("y", function(d) { return d.dy / 2; })
      .attr("dy", ".35em")
      .attr("text-anchor", "end")
      .attr("transform", null)
      .text(function(d) { return d.name; })
    .filter(function(d) { return d.x < width / 2; })
      .attr("x", 6 + sankey.nodeWidth())
      .attr("text-anchor", "start");

  function dragmove(d) {
    d3.select(this).attr("transform", "translate(" + d.x + "," + (d.y = Math.max(0, Math.min(height - d.dy, d3.event.y))) + ")");
    sankey.relayout();
    link.attr("d", path);
  }



});

</script>

Answer 1

This is called a brush in d3.js.

You need to register a brush object, which takes care of computing the "brushed" area (access it via brush.extend), and to which you can associate events (brush start, brush, brush end) to update your drawing accordingly.

See documentation and examples at https://github.com/mbostock/d3/wiki/SVG-Controls