D3 Examples - Neighborhood Pull

Neighborhood Pull
This example demonstrates applying d3-drag to a force-directed graph computed using d3-force. When the drag gesture starts, the targetted node is fixed to the pointer; it is released when the gesture ends.
Double-click to select a neighborhood, which will react to the dragged node.
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<!DOCTYPE html>
<meta charset="utf-8">
<style>
​
  .links line {
    stroke: #aaa;
  }
​
  .nodes circle {
    pointer-events: all;
    stroke: none;
    stroke-width: 40px;
  }
​
  .nodes circle.fixed {
    fill: #fe3838;
  }
  
  .nodes circle.selected {
    stroke: #000000;
    stroke-width: 1.5px;
  }
  .nodes text{
    fill: #666;
    font-family: Helvetica
    }
  
</style>
<svg width="960" height="600"></svg>
<script src="https://d3js.org/d3.v4.min.js"></script>
<script>
​
var svg = d3.select("svg"),
    width = +svg.attr("width"),
    height = +svg.attr("height");
​
  var neighborhood = [];
  
var simulation = d3.forceSimulation()
    .force("link", d3.forceLink().id(function(d) { return d.id; }))
    .force("charge", d3.forceManyBody())
    .force("center", d3.forceCenter(width / 2, height / 2));
​
d3.json("miserables.json", function(error, graph) {
  if (error) throw error;
​
  var link = svg.append("g")
      .attr("class", "links")
    .selectAll("line")
    .data(graph.links)
    .enter().append("line");
​
  var node = svg.append("g")
      .attr("class", "nodes")
    .selectAll("circle")
    .data(graph.nodes)
    .enter().append("circle")
      .attr("r", 5.0)
      .attr("id", function(d) { return d.id; })
      .on("click", selectedNode)
      .on("dblclick", selectedNeighborhood)
      .call(d3.drag()
          .on("start", dragstarted)
          .on("drag", dragged)
          .on("end", dragended))
  
  ;
​
  node.append("text")
        .attr("dx", 6)
      .text(function(d) { return d.id; });
​
  simulation
      .nodes(graph.nodes)
      .on("tick", ticked);
  
  simulation
    .on("end", settled);
​
  simulation.force("link")
      .links(graph.links);
​
  function ticked() {
    link
        .attr("x1", function(d) { return d.source.x; })
        .attr("y1", function(d) { return d.source.y; })
        .attr("x2", function(d) { return d.target.x; })
        .attr("y2", function(d) { return d.target.y; });
​
    node
        .attr("cx", function(d) { return d.x; })
        .attr("cy", function(d) { return d.y; })
            .classed("fixed", function(d) { 
            return (d.vx < 0.02) && (d.vy < 0.02);
            })
    ;
  };
  
  function settled() {
    node.data().forEach( settle );
  };
  
  function settle(d) {
    d.fx = d.x; 
    d.fy = d.y; 
    d3.select('#'+d.id).classed("fixed", true);
  }
  
  function selectedNode(d) {
    if (d3.event.defaultPrevented) return; // dragged
​
    d3.select(this).classed("selected", true);
  }
  
  function selectedNeighborhood(d) {
    if (d3.event.defaultPrevented) return; // dragged
    neighborhood = [];
    neighborhood.push(d);
    link.data().forEach( function(l) {
      if (l.source == d) {
        neighborhood.push(l.target);
      } else if (l.target == d) {
        neighborhood.push(l.source);
      }
    })
    neighborhood.forEach(function(d) {    
        d3.select('#'+d.id).classed("selected", true);
    })
  }
​
  
});
  
​
function dragstarted(d) {
  if (!d3.event.active) simulation.alphaTarget(0.3).restart();
  neighborhood.forEach(function(n) {    
    n.fx = null;
    n.fy = null;
  });
​
  d.fx = d.x;
  d.fy = d.y;
}
​
function dragged(d) {
  d.fx = d3.event.x;
  d.fy = d3.event.y;
}
​
function dragended(d) {
  if (!d3.event.active) simulation.alphaTarget(0);
  neighborhood.forEach(function(n) {    
      d3.select('#'+n.id).classed("selected", false);
​
  });
​
​
}
​
</script>
​
    