在树布局d3中引入箭头

Question

我必须实现树形布局，如http://mbostock.github.io/d3/talk/20110921/parent-foci.html

它应该有从父到子的箭头，或者在某些情况下，箭头也应该从子指向父…如http://jsfiddle.net/mdml/ncwuej9j/

svg.append("svg:defs").selectAll("marker")
    .data(["end"])      // Different link/path types can be defined here
  .enter().append("svg:marker")    // This section adds in the arrows
    .attr("id", String)
    .attr("viewBox", "0 -5 10 10")
    .attr("refX", 15)
    .attr("refY", -1.5)
    .attr("markerWidth", 6)
    .attr("markerHeight", 6)
    .attr("orient", "auto")
  .append("svg:path")
    .attr("d", "M0,-5L10,0L0,5");

看起来这是用于箭头，但我不知道如何在树布局中使用

已经明白json格式是不同的…如果可能的话。我是D3的新手，所以大家帮帮我。

Answer 1

对于您共享的代码，您唯一需要在路径末尾放置箭头的是在路径上添加marker-end:

.attr("marker-end", "url(#end)");

例如，从d3noob: http://bl.ocks.org/d3noob/8326869获取这个树布局。它没有箭头，因为你可以很容易地检查。那么，让我们把它们加起来。

第一步是附加defs，如您所共享的:

svg.append("svg:defs").selectAll("marker")
.data(["end"])      // Different link/path types can be defined here
.enter().append("svg:marker")    // This section adds in the arrows
.attr("id", String)
.attr("viewBox", "0 -5 10 10")
.attr("refX", 15)
.attr("refY", -1.5)
.attr("markerWidth", 6)
.attr("markerHeight", 6)
.attr("orient", "auto")
.append("svg:path")
.attr("d", "M0,-5L10,0L0,5");

然后，在路径的末尾(根据您没有提供的实际代码更改):

link.enter().insert("path", "g")
    .attr("class", "link")
    .attr("d", diagonal)
    .attr("marker-end", "url(#end)");

下面是一个工作演示:

var treeData = [
  {
    "name": "Top Level",
    "parent": "null",
    "children": [
      {
        "name": "Level 2: A",
        "parent": "Top Level",
        "children": [
          {
            "name": "Son of A",
            "parent": "Level 2: A"
          },
          {
            "name": "Daughter of A",
            "parent": "Level 2: A"
          }
        ]
      },
      {
        "name": "Level 2: B",
        "parent": "Top Level"
      }
    ]
  }
];
// ************** Generate the tree diagram	 *****************
var margin = {top: 40, right: 120, bottom: 20, left: 120},
	width = 960 - margin.right - margin.left,
	height = 500 - margin.top - margin.bottom;
	
var i = 0;
var tree = d3.layout.tree()
	.size([height, width]);
var diagonal = d3.svg.diagonal()
	.projection(function(d) { return [d.x, d.y]; });
var svg = d3.select("body").append("svg")
	.attr("width", width + margin.right + margin.left)
	.attr("height", height + margin.top + margin.bottom)
  .append("g")
	.attr("transform", "translate(" + margin.left + "," + margin.top + ")");
root = treeData[0];
  
update(root);
function update(source) {
svg.append("svg:defs").selectAll("marker")
    .data(["end"])      // Different link/path types can be defined here
  .enter().append("svg:marker")    // This section adds in the arrows
    .attr("id", String)
    .attr("viewBox", "0 -5 10 10")
    .attr("refX", 18)
    .attr("refY", 0)
    .attr("markerWidth", 6)
    .attr("markerHeight", 6)
    .attr("orient", "auto")
  .append("svg:path")
    .attr("d", "M0,-5L10,0L0,5");
  // Compute the new tree layout.
  var nodes = tree.nodes(root).reverse(),
	  links = tree.links(nodes);
  // Normalize for fixed-depth.
  nodes.forEach(function(d) { d.y = d.depth * 100; });
  // Declare the nodes…
  var node = svg.selectAll("g.node")
	  .data(nodes, function(d) { return d.id || (d.id = ++i); });
  // Enter the nodes.
  var nodeEnter = node.enter().append("g")
	  .attr("class", "node")
	  .attr("transform", function(d) { 
		  return "translate(" + d.x + "," + d.y + ")"; });
  nodeEnter.append("circle")
	  .attr("r", 10)
	  .style("fill", "#fff");
  nodeEnter.append("text")
	  .attr("y", function(d) { 
		  return d.children || d._children ? -18 : 18; })
	  .attr("dy", ".35em")
	  .attr("text-anchor", "middle")
	  .text(function(d) { return d.name; })
	  .style("fill-opacity", 1);
  // Declare the links…
  var link = svg.selectAll("path.link")
	  .data(links, function(d) { return d.target.id; });
  // Enter the links.
  link.enter().insert("path", "g")
	  .attr("class", "link")
	  .attr("d", diagonal)
		.attr("marker-end", "url(#end)");
}

	.node circle {
	  fill: #fff;
	  stroke: steelblue;
	  stroke-width: 3px;
	}
	.node text { font: 12px sans-serif; }
	.link {
	  fill: none;
	  stroke: #ccc;
	  stroke-width: 2px;
	}

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