d3.js：如何在强制布局中更新链接数据时删除节点答案

【问题标题】：d3.js: How to remove nodes when link-data updates in a force layoutd3.js：如何在强制布局中更新链接数据时删除节点
【发布时间】：2014-01-30 23:53:13
【问题描述】：

我正在使用强制布局图来显示网络，但更新数据时出现问题。

我已经检查了How to update elements of D3 force layout when the underlying data changes，当然还有来自 D3.js 的“mbostock”的“修改强制布局”以及“常规更新模式”（不幸的是，我只能最多发布两个链接...）。

我的代码基于“Mobile Patent Suits”示例，并进行了一些修改和不同之处。你可以在这里查看我的完整代码：

<!DOCTYPE html>
<meta charset="utf-8">
<style>

.link {
    fill: none;
    stroke: #666;
    stroke-width: 1.5px;
}

#licensing {
    fill: green;
}

.link.licensing {
    stroke: green;
}

.link.resolved {
    stroke-dasharray: 0,2 1;
}

circle {
    fill: #ccc;
    stroke: #333;
    stroke-width: 1.5px;
}

text {
    font: 10px sans-serif;
    pointer-events: none;
    text-shadow: 0 1px 0 #fff, 1px 0 0 #fff, 0 -1px 0 #fff, -1px 0 0 #fff;
}

</style>
<body>
    <!-- add an update button -->
    <div id="update">
        <input name="updateButton" type="button" value="Update" onclick="newData()"/>
    </div>
    <script src="http://d3js.org/d3.v3.min.js"></script>
    <script>

    var width = 960,
        height = 500;

    var force = d3.layout.force()
        .size([width, height])
        .linkDistance(60)
        .charge(-300)
        .on("tick", tick);

    var svg = d3.select("body").append("svg")
        .attr("width", width)
        .attr("height", height)
        .style("border", "1px solid black");

    var dataset = [
                 {source: "Microsoft", target: "Amazon", type: "licensing"},
                 {source: "Microsoft", target: "HTC", type: "licensing"},
                 {source: "Samsung", target: "Apple", type: "suit"},
                 {source: "Motorola", target: "Apple", type: "suit"},
                 {source: "Nokia", target: "Apple", type: "resolved"},
                 {source: "HTC", target: "Apple", type: "suit"},
                 {source: "Kodak", target: "Apple", type: "suit"},
                 {source: "Microsoft", target: "Barnes & Noble", type: "suit"},
                 {source: "Microsoft", target: "Foxconn", type: "suit"},
                 {source: "Oracle", target: "Google", type: "suit"},
                 {source: "Apple", target: "HTC", type: "suit"},
                 {source: "Microsoft", target: "Inventec", type: "suit"},
                 {source: "Samsung", target: "Kodak", type: "resolved"},
                 {source: "LG", target: "Kodak", type: "resolved"},
                 {source: "RIM", target: "Kodak", type: "suit"},
                 {source: "Sony", target: "LG", type: "suit"},
                 {source: "Kodak", target: "LG", type: "resolved"},
                 {source: "Apple", target: "Nokia", type: "resolved"},
                 {source: "Qualcomm", target: "Nokia", type: "resolved"},
                 {source: "Apple", target: "Motorola", type: "suit"},
                 {source: "Microsoft", target: "Motorola", type: "suit"},
                 {source: "Motorola", target: "Microsoft", type: "suit"},
                 {source: "Huawei", target: "ZTE", type: "suit"},
                 {source: "Ericsson", target: "ZTE", type: "suit"},
                 {source: "Kodak", target: "Samsung", type: "resolved"},
                 {source: "Apple", target: "Samsung", type: "suit"},
                 {source: "Kodak", target: "RIM", type: "suit"},
                 {source: "Nokia", target: "Qualcomm", type: "suit"}
                 ];

   var path = svg.append("g").selectAll("path"),
       circle = svg.append("g").selectAll("circle"),
       text = svg.append("g").selectAll("text"),
       marker = svg.append("defs").selectAll("marker");

   var nodes = {};

   update(dataset);

   function newData()
   {
        var newDataset = [
                    {source: "Microsoft", target: "Amazon", type: "licensing"},
                    {source: "Microsoft", target: "HTC", type: "licensing"},
                    {source: "Samsung", target: "Apple", type: "suit"},
                    ];

        update(newDataset);
   }

   function update(links)
   {
        // Compute the distinct nodes from the links.
        links.forEach(function(link)
        {
            link.source = nodes[link.source] || (nodes[link.source] = {name: link.source});
            link.target = nodes[link.target] || (nodes[link.target] = {name: link.target});
        });

        force
            .nodes(d3.values(nodes))
            .links(links)
            .start();

        // -------------------------------

        // Compute the data join. This returns the update selection.
        marker = marker.data(["suit", "licensing", "resolved"]);

        // Remove any outgoing/old markers.
        marker.exit().remove();

        // Compute new attributes for entering and updating markers.
        marker.enter().append("marker")
           .attr("id", function(d) { return d; })
           .attr("viewBox", "0 -5 10 10")
           .attr("refX", 15)
           .attr("refY", -1.5)
           .attr("markerWidth", 6)
           .attr("markerHeight", 6)
           .attr("orient", "auto")
           .append("line") // use ".append("path") for 'arrows'
           .attr("d", "M0,-5L10,0L0,5");

        // -------------------------------

        // Compute the data join. This returns the update selection.
        path = path.data(force.links());

        // Remove any outgoing/old paths.
        path.exit().remove();

        // Compute new attributes for entering and updating paths.
        path.enter().append("path")
           .attr("class", function(d) { return "link " + d.type; })
           .attr("marker-end", function(d) { return "url(#" + d.type + ")"; });

        // -------------------------------

        // Compute the data join. This returns the update selection.
        circle = circle.data(force.nodes());

        // Add any incoming circles.
        circle.enter().append("circle");

        // Remove any outgoing/old circles.
        circle.exit().remove();

        // Compute new attributes for entering and updating circles.
        circle
           .attr("r", 6)
           .call(force.drag);

        // -------------------------------

        // Compute the data join. This returns the update selection.
        text = text.data(force.nodes());

        // Add any incoming texts.
        text.enter().append("text");

        // Remove any outgoing/old texts.
        text.exit().remove();

        // Compute new attributes for entering and updating texts.
        text
           .attr("x", 8)
           .attr("y", ".31em")
           .text(function(d) { return d.name; });
    }

    // Use elliptical arc path segments to doubly-encode directionality.
    function tick()
    {
       path.attr("d", linkArc);
       circle.attr("transform", transform);
       text.attr("transform", transform);
    }

    function linkArc(d)
    {
       var dx = d.target.x - d.source.x,
           dy = d.target.y - d.source.y,
           dr = Math.sqrt(dx * dx + dy * dy);
       return "M" + d.source.x + "," + d.source.y + "A" + dr + "," + dr + " 0 0,1 " + d.target.x + "," + d.target.y;
    }

    function transform(d)
    {
       return "translate(" + d.x + "," + d.y + ")";
    }

    </script>

我的代码的 JSFiddle 可以在这里找到：http://jsfiddle.net/5m8a9/

按下“更新”按钮后，我想动态更新我的图表。到目前为止，问题是，只有路径会被更新，而不是圆圈或文本（一些圆圈和相应的文本仍然存在，不会被删除），如您所见我的 JSFiddle 链接。最近几天我试图找出问题所在，但没有成功。

我缺少什么以及如何使我的代码按方面工作？

如果有人能提供帮助，我将永远感激不尽。

已编辑以添加 @AmeliaBR 提供的最终解决方案：

这是我最终解决方案的漏洞代码：

<!DOCTYPE html>
<meta charset="utf-8">
<style>

.link {
    fill: none;
    stroke: #666;
    stroke-width: 1.5px;
}

#licensing {
    fill: green;
}

.link.licensing {
    stroke: green;
}

.link.resolved {
    stroke-dasharray: 0,2 1;
}

circle {
    fill: #ccc;
    stroke: #333;
    stroke-width: 1.5px;
}

text {
    font: 10px sans-serif;
    pointer-events: none;
    text-shadow: 0 1px 0 #fff, 1px 0 0 #fff, 0 -1px 0 #fff, -1px 0 0 #fff;
}

    </style>
<body>
    <!-- add an update button -->
    <div id="update">
        <input name="updateButton" type="button" value="Update" onclick="newData()"/>
    </div>
    <script src="http://d3js.org/d3.v3.min.js"></script>
    <script>

    var width = 960,
        height = 500;

    var force = d3.layout.force()
        .size([width, height])
        .linkDistance(60)
        .charge(-300)
        .on("tick", tick);

    var svg = d3.select("body").append("svg")
        .attr("width", width)
        .attr("height", height)
        .style("border", "1px solid black");

    var dataset = [
                   {source: "Microsoft", target: "Amazon", type: "licensing"},
                   {source: "Microsoft", target: "HTC", type: "licensing"},
                   {source: "Samsung", target: "Apple", type: "suit"},
                   {source: "Motorola", target: "Apple", type: "suit"},
                   {source: "Nokia", target: "Apple", type: "resolved"},
                   {source: "HTC", target: "Apple", type: "suit"},
                   {source: "Kodak", target: "Apple", type: "suit"},
                   {source: "Microsoft", target: "Barnes & Noble", type: "suit"},
                   {source: "Microsoft", target: "Foxconn", type: "suit"},
                   {source: "Oracle", target: "Google", type: "suit"},
                   {source: "Apple", target: "HTC", type: "suit"},
                   {source: "Microsoft", target: "Inventec", type: "suit"},
                   {source: "Samsung", target: "Kodak", type: "resolved"},
                   {source: "LG", target: "Kodak", type: "resolved"},
                   {source: "RIM", target: "Kodak", type: "suit"},
                   {source: "Sony", target: "LG", type: "suit"},
                   {source: "Kodak", target: "LG", type: "resolved"},
                   {source: "Apple", target: "Nokia", type: "resolved"},
                   {source: "Qualcomm", target: "Nokia", type: "resolved"},
                   {source: "Apple", target: "Motorola", type: "suit"},
                   {source: "Microsoft", target: "Motorola", type: "suit"},
                   {source: "Motorola", target: "Microsoft", type: "suit"},
                   {source: "Huawei", target: "ZTE", type: "suit"},
                   {source: "Ericsson", target: "ZTE", type: "suit"},
                   {source: "Kodak", target: "Samsung", type: "resolved"},
                   {source: "Apple", target: "Samsung", type: "suit"},
                   {source: "Kodak", target: "RIM", type: "suit"},
                   {source: "Nokia", target: "Qualcomm", type: "suit"}
                   ];

    var path = svg.append("g").selectAll("path"),
    circle = svg.append("g").selectAll("circle"),
    text = svg.append("g").selectAll("text"),
    marker = svg.append("defs").selectAll("marker");

    var nodes = {};

    update(dataset);

    function newData()
    {
        var newDataset = [
                         {source: "Microsoft", target: "Amazon", type: "licensing"},
                         {source: "Microsoft", target: "HTC", type: "licensing"},
                         {source: "Samsung", target: "Apple", type: "suit"},
                         ];

        update(newDataset);
    }

    function update(links)
    {
        d3.values(nodes).forEach(function(aNode){ aNode.linkCount = 0;});
            // Reset the link count for all existing nodes by
            // creating an array out of the nodes list, and then calling a function
            // on each node to set the linkCount property to zero.

        // Compute the distinct nodes from the links.
        links.forEach(function(link)
        {
            link.source = nodes[link.source] || (nodes[link.source] = {name: link.source, linkCount:0});    // initialize new nodes with zero links
            link.source.linkCount++;
                // record this link on the source node, whether it was just initialized
                // or already in the list, by incrementing the linkCount property
                // (remember, link.source is just a reference to the node object in the
                // nodes array, when you change its properties you change the node itself.)

            link.target = nodes[link.target] || (nodes[link.target] = {name: link.target, linkCount:0});    // initialize new nodes with zero links

            link.target.linkCount++;
        });

        d3.keys(nodes).forEach(
            // create an array of all the current keys(names) in the node list,
            // and then for each one:

            function (nodeKey)
            {
                if (!nodes[nodeKey].linkCount)
                {
                    // find the node that matches that key, and check it's linkCount value
                    // if the value is zero (false in Javascript), then the ! (NOT) operator
                    // will reverse that to make the if-statement return true,
                    // and the following will execute:

                    delete(nodes[nodeKey]);
                        //this deletes the object AND its key from the nodes array
                 }
             }
         );

        force
            .nodes(d3.values(nodes))
            .links(links)
            .start();

        // -------------------------------

        // Compute the data join. This returns the update selection.
        marker = marker.data(["suit", "licensing", "resolved"]);

        // Remove any outgoing/old markers.
        marker.exit().remove();

        // Compute new attributes for entering and updating markers.
        marker.enter().append("marker")
            .attr("id", function(d) { return d; })
            .attr("viewBox", "0 -5 10 10")
            .attr("refX", 15)
            .attr("refY", -1.5)
            .attr("markerWidth", 6)
            .attr("markerHeight", 6)
            .attr("orient", "auto")
            .append("line") // use ".append("path") for 'arrows'
            .attr("d", "M0,-5L10,0L0,5");

        // -------------------------------

        // Compute the data join. This returns the update selection.
        path = path.data(force.links());

        // Remove any outgoing/old paths.
        path.exit().remove();

        // Compute new attributes for entering and updating paths.
        path.enter().append("path")
            .attr("class", function(d) { return "link " + d.type; })
            .attr("marker-end", function(d) { return "url(#" + d.type + ")"; });

        // -------------------------------

        // Compute the data join. This returns the update selection.
        circle = circle.data(force.nodes());

        // Add any incoming circles.
        circle.enter().append("circle");

        // Remove any outgoing/old circles.
        circle.exit().remove();

        // Compute new attributes for entering and updating circles.
        circle
            .attr("r", 6)
            .call(force.drag);

        // -------------------------------

        // Compute the data join. This returns the update selection.
        text = text.data(force.nodes());

        // Add any incoming texts.
        text.enter().append("text");

        // Remove any outgoing/old texts.
        text.exit().remove();

        // Compute new attributes for entering and updating texts.
        text
            .attr("x", 8)
            .attr("y", ".31em")
            .text(function(d) { return d.name; });
    }

    // Use elliptical arc path segments to doubly-encode directionality.
    function tick()
    {
        path.attr("d", linkArc);
        circle.attr("transform", transform);
        text.attr("transform", transform);
    }

    function linkArc(d)
    {
        var dx = d.target.x - d.source.x,
            dy = d.target.y - d.source.y,
            dr = Math.sqrt(dx * dx + dy * dy);
        return "M" + d.source.x + "," + d.source.y + "A" + dr + "," + dr + " 0 0,1 " + d.target.x + "," + d.target.y;
    }

    function transform(d)
    {
        return "translate(" + d.x + "," + d.y + ")";
    }

    </script>

【问题讨论】：

标签： javascript graph d3.js force-layout

【解决方案1】：

一般的节点-链接图结构可以有没有链接的节点，就像它可以有一个、两个或数百个链接的节点一样。您的更新方法会替换链接的数据，但不会查看节点数据以删除不再附加任何链接的节点数据。

您目前已经按照他们的方式进行了设置，但是，有一个相当简单的解决方法。照原样，您从数据集中初始化链接，并将节点初始化为空。然后在你的更新方法的这一部分：

links.forEach(function(link)
        {
            link.source = nodes[link.source] 
                          || (nodes[link.source] = {name: link.source});

            link.target = nodes[link.target] 
                          || (nodes[link.target] = {name: link.target});
        });

在首先检查它是否已经在列表中之后，将提到的所有节点作为链接的源或目标添加到节点列表中。

(如果它不在列表中，nodes[link.source] 将返回 null，因此|| OR 运算符将启动并评估语句的后半部分，创建对象，将其添加到节点列表，然后将其连接到链接对象。）

现在，当您第一次运行更新方法时，它会用数据填充节点列表。但是，第二次时，节点列表已经满了，您无需执行任何操作来删除任何节点。

简单的解决方法是在更新方法开始时将节点列表重置为空对象 (nodes={};)。然后，只会将当前链接集中的节点添加回，因此当您重新计算圆圈和文本上的数据连接时，所有未使用的节点将被放入 .exit() 选择并删除。

但是，我应该提一下，如果您要更新很多，并且每次只更改几个对象，还有其他方法可以做到这一点，需要更多代码，但更新速度会更快.此版本每次都重新创建所有节点和链接数据对象。如果您有很多（数百个）复杂的数据节点并且每次更新只更改几个，那么为您的节点对象添加一个额外的属性来跟踪连接了多少链接并且只重置可能是值得的在您的更新方法开始时。然后，您可以使用过滤器来确定要在数据连接中包含哪些节点对象。

编辑添加：

这是我用于更保守的更新功能的方法（相对于数据的完全重置）。这不是唯一的选择，但它没有太多开销：

第一步（在更新方法中），将所有节点标记为零链接：

d3.values(nodes).forEach(function(aNode){ aNode.linkCount = 0;}); 
   //Reset the link count for all existing nodes by
   //creating an array out of the nodes list, and then calling a function
   //on each node to set the linkCount property to zero.

第二步，改links.forEach()方法记录每个节点的链接数：

links.forEach(function(link)
    {
     link.source = nodes[link.source] 
                      || (nodes[link.source] = {name: link.source, linkCount:0});
                                    //initialize new nodes with zero links

     link.source.linkCount++;
        // record this link on the source node, whether it was just initialized
        // or already in the list, by incrementing the linkCount property
        // (remember, link.source is just a reference to the node object in the 
        // nodes array, when you change its properties you change the node itself.)

     link.target = /* and then do the same for the target node */
    });

第三步，选项一，使用filter 仅包含至少有一个链接的节点：

force
    .nodes( d3.values(nodes).filter(function(d){ return d.linkCount;}) )
      //Explanation: d3.values() turns the object-list of nodes into an array.
      //.filter() goes through that array and creates a new array consisting of 
      //the nodes that return TRUE when passed to the callback function.  
      //The function just returns the linkCount of that node, which Javascript 
      //interprets as false if linkCount is zero, or true otherwise.
    .links(links)
    .start();

请注意，此不会从nodes 列表中删除未使用的节点，它只会过滤它们以防止传递给布局。如果您不希望再次使用这些节点，则需要将它们从节点列表中实际删除。

第三步，选项二，扫描节点列表，删除所有链接为零的节点：

d3.keys(nodes).forEach(
   //create an array of all the current keys(names) in the node list, 
   //and then for each one:

   function (nodeKey) {
       if (!nodes[nodeKey].linkCount) {
         // find the node that matches that key, and check it's linkCount value
         // if the value is zero (false in Javascript), then the ! (NOT) operator
         // will reverse that to make the if-statement return true, 
         // and the following will execute:

           delete(nodes[nodeKey]); 
             //this deletes the object AND its key from the nodes array
       }

   }//end of function

); //end of forEach method

  /*then add the nodes list to the force layout object as before, 
     no filter needed since the list only includes the nodes you want*/

【讨论】：

感谢您的解释。虽然我没有理解所有内容，但它有助于我进一步理解它。使用空对象 (nodes={};) 的“简单修复”有效，BUT 正如您已经提到的，这不是我所期望/假设的它应该如何工作（这更像是“重新加载”而不是'更新'）。我怎样才能实现你所说的数据和图表的“真实”更新？你能这么好心并给我一些代码（使用我的例子）吗？那真的很棒，因为我对“简单的修复”还不满意。
@user3186482 这在很大程度上取决于您的真实数据的格式，以及您是想在每次更新时从数据中删除未使用的节点，还是只是暂时从显示中过滤掉它们。但我会在答案的末尾添加更多提示。
最后，我想实现以下目标：a) 侦听 websocket 并获取带有source、target 和 (IP-) 的 CSV 文件prefix（使用 push 方法）b) 解析这个 CSV 文件并绘制图表（我想我用上面的代码管理到这里，对吗？) c) 监听下一个 CSV 文件（可能只有少量更改，但无论如何 CSV 文件可能很大 -> 数百或数千节点）。直接回答您的问题：我想我将始终删除未使用的节点。我希望我的解释足够清楚？！如果不告诉我，我会尝试更详细地解释它
好吧，添加的代码应该向您展示如何根据链接列表更新/删除节点。您必须弄清楚如何扫描庞大的 CSV 文件并有效地更新链接数据。但我要警告你，无论你使用什么代码，数千个节点都可能导致性能问题——在强制算法的每个“滴答”中都有很多节点要移动。
非常感谢您的分步指导和出色的解释。一切都像一个魅力（我更喜欢使用选项二）。尽管我并不真正理解选项一和选项二“幕后”之间的区别。我将其视为性能问题。稍后我会将我的完整代码添加到我的开场问题中，这样每个人都可以从完全/最终的解决方案中受益。是否有任何提示我可以如何处理来自 CSV 文件的如此大数据（多达数百或数千个节点）（这里似乎非常滞后）？当然，任何代码都将不胜感激如何准确地做到这一点。