我只想显示按可折叠树的大小排序的前N个孩子。我使用的是collapsible tree example，但我不想显示所有的孩子，而只希望显示前5名或我指定的N。
我可以想到的一个方法是保留2个数据副本。一个副本将包含所有子代，第二个副本将仅包含前N个子代。然后仅用第二个副本构建树。我不知道是否还有另一种更好的d3.js方法。
var data = {
"key": "parent",
"size": 100,
"children" :[
{
"key" : "child1",
"size": 10
},
{
"key" : "child2",
"size": 4
},
{
"key" : "child3",
"size": 1
},
{
"key" : "child4",
"size": 2
},
{
"key" : "child5",
"size": 3
},
{
"key" : "child6",
"size": 20
},
{
"key" : "child7",
"size": 4
},
{
"key" : "child8",
"size": 1
},
{
"key" : "child9",
"size": 5
},
{
"key" : "child10",
"size": 50
}
]
};
var margin = {top: 20, right: 120, bottom: 20, left: 120},
width = 1060 - margin.right - margin.left,
height = 1200 - margin.top - margin.bottom;
var i = 0,
duration = 750,// animation duration
root;// stores the tree structure in json format
var tree = d3.layout.tree()
.size([height, width]);
var edge_weight = d3.scale.linear()
.domain([0, 100])
.range([0, 100]);
var diagonal = d3.svg.diagonal()
.projection(function(d) { return [d.y, d.x]; });
// adding the svg to the html structure
var svg = d3.select("div#viz").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 + ")");
edge_weight.domain([0,data.size]);
root = data;
root.x0 = height / 2;
root.y0 = 0;
update(root);
d3.select(self.frameElement).style("height", "800px");
/**
* Updates the node.
* cloppases and expands the node bases on the structure of the source
* all 'children' nodes are expanded and '_children' nodes collapsed
* @param {json structure} source
*/
function update(source) {
// 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 * 180; });
// Update the nodes…
var node = svg.selectAll("g.node")
.data(nodes, function(d) { return d.id || (d.id = ++i); });
// Enter any new nodes at the parent's previous position.
var nodeEnter = node.enter().append("g")
.attr("class", "node")
.attr("transform", function(d) { return "translate(" + source.y0 + "," + source.x0 + ")"; })
.on("click", click);
nodeEnter.append("circle")
.attr("r", 1e-6)
.style("fill", function(d) { return d._children ? "lightsteelblue" : "#fff"; });
nodeEnter.append("text")
.attr("x", function(d) { return d.children || d._children ? -10 : 10; })
.attr("dy", ".35em")
.attr("text-anchor", function(d) { return d.children || d._children ? "end" : "start"; })
.text(function(d) { return d.key; })
.style("fill-opacity", 1e-6);
// Transition nodes to their new position.
var nodeUpdate = node.transition()
.duration(duration)
.attr("transform", function(d) { return "translate(" + d.y + "," + d.x + ")"; });
nodeUpdate.select("circle")
.attr("r", function(d){ return edge_weight(d.size/2);})
.style("fill", function(d) {
return d._children ? "lightsteelblue" : "#fff"; });
nodeUpdate.select("text")
.style("fill-opacity", 1);
// Transition exiting nodes to the parent's new position.
var nodeExit = node.exit().transition()
.duration(duration)
.attr("transform", function(d) { return "translate(" + source.y + "," + source.x + ")"; })
.remove();
nodeExit.select("circle")
.attr("r", 1e-6);
nodeExit.select("text")
.style("fill-opacity", 1e-6);
// Update the links…
var link = svg.selectAll("path.link")
.data(links, function(d) { return d.target.id; });
// Enter any new links at the parent's previous position.
link.enter().insert("path", "g")
.attr("class", "link")
.attr("stroke-width", function(d){
return 1;
})
.attr("d", function(d) {
var o = {x: source.x0, y: source.y0};
return diagonal({source: o, target: o});
})
.attr("stroke", function(d){
return '#0950D0';});
// Transition links to their new position.
link.transition()
.duration(duration)
.attr("d", function(d){
/* calculating the top shift */
var source = {x: d.source.x - edge_weight(calculateLinkSourcePosition(d)), y: d.source.y};
var target = {x: d.target.x, y: d.target.y};
return diagonal({source: source, target: target});
})
.attr("stroke-width", function(d){
return edge_weight(d.target.size);
});
// Transition exiting nodes to the parent's new position.
link.exit().transition()
.duration(duration)
.attr("d", function(d) {
var o = {x: source.x, y: source.y};
return diagonal({source: o, target: o});
})
.remove();
// Stash the old positions for transition.
nodes.forEach(function(d) {
d.x0 = d.x;
d.y0 = d.y;
});
}
/**
* Calculates the source y-axis position of the link.
* @param {json structure} link
*/
function calculateLinkSourcePosition(link) {
targetID = link.target.id;
var childrenNumber = link.source.children.length;
var widthAbove = 0;
for (var i = 0; i < childrenNumber; i++)
{
if (link.source.children[i].id == targetID)
{
// we are done
widthAbove = widthAbove + link.source.children[i].size/2;
break;
}else {
// keep adding
widthAbove = widthAbove + link.source.children[i].size
}
}
return link.source.size/2 - widthAbove;
}
/*
* Toggle children on click.
* @param {node} d
*/
function click(d) {
if (d.children) {
d._children = d.children;
d.children = null;
} else {
d.children = d._children;
d._children = null;
}
update(d);
}.node {
cursor: pointer;
}
.node circle {
fill: #fff;
stroke: steelblue;
stroke-width: 1.5px;
}
.node text {
font: 10px sans-serif;
}
.link {
fill: none;
/*stroke: steelblue;*/
opacity: 0.3;
/*stroke-width: 1.5px;*/
}
#levels{
margin-left: 120px;
}<!DOCTYPE html>
<meta charset="utf-8">
<script src="https://cdnjs.cloudflare.com/ajax/libs/d3/3.5.17/d3.min.js"></script>
<body>
<div id="viz"></div>
</body>
预先感谢您的帮助。
答案 0 :(得分：0)
在生成树形图之前，可以使用Javascript数组函数sort和slice将数据限制为每个节点的前N个子节点。为此，请在函数update()的顶部包含以下代码：
//...
function update(source) {
function topN(node, N) {
if (node.children) {
// The node has children
node.children.sort(d3.descending); // Array sorted in-place
node.children = node.children.slice(0, N);
// Now run the function on each child:
node.children.forEach(function (x) {
topN(x, N);
});
}
}
topN(source, 5);
// Compute the new tree layout.
//...