动态插入的 d3 力图未展开

Question

附加的代码段包含 official d3 force graph example code 的修改版本。当我立即插入图表时，一切都按预期进行。但是，如果我动态插入图形（您可以通过在演示中按 Clear and Redraw 来完成），节点不会以相同的方式展开。有时它们甚至停留在 svg 的左上角。

我发现的一个技巧是在插入图表后添加 simulation.alphaTarget(1).restart()。不幸的是，这需要更长的时间才能达到稳定的输出，并可能导致残余震颤（或旋转）。

如何使动态插入的图形具有在页面加载时立即插入图形的行为而不需要我的 hack？

var svg = d3.select("svg"),
    width = +svg.attr("width"),
    height = +svg.attr("height");

var color = d3.scaleOrdinal(d3.schemeCategory20);

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));

// I wrapped the d3.json invocation in this function
function drawGraph() {
  d3.json("https://gist.githubusercontent.com/mbostock/4062045/raw/5916d145c8c048a6e3086915a6be464467391c62/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")
        .attr("stroke-width", function(d) { return Math.sqrt(d.value); });

    var node = svg.append("g")
        .attr("class", "nodes")
      .selectAll("circle")
      .data(graph.nodes)
      .enter().append("circle")
        .attr("r", 5)
        .attr("fill", function(d) { return color(d.group); })
        .call(d3.drag()
            .on("start", dragstarted)
            .on("drag", dragged)
            .on("end", dragended));

    node.append("title")
        .text(function(d) { return d.id; });

    simulation
        .nodes(graph.nodes)
        .on("tick", ticked);

    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; });
    }
  });
}

// When I call it hear, all is well (as you would expect).
drawGraph()

// But when I clear and redraw it (by pressing a button), the nodes
// don't spread out.
function clearRedraw() {
  d3.selectAll("svg > *").remove()
  drawGraph()
}

function hackySolution() {
  d3.selectAll("svg > *").remove()
  drawGraph()
  simulation.alphaTarget(1).restart()
}


function dragstarted(d) {
  if (!d3.event.active) simulation.alphaTarget(0.3).restart();
  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);
  d.fx = null;
  d.fy = null;
}

.links line {
  stroke: #999;
  stroke-opacity: 0.6;
}

.nodes circle {
  stroke: #fff;
  stroke-width: 1.5px;
}

<!DOCTYPE html>
<html>
<head>
  <meta charset="utf-8">
  <meta name="viewport" content="width=device-width">
  <title>JS Bin</title>
</head>
<body>
  <button onclick="clearRedraw()">Clear And Redraw</button>
  <button onclick="hackySolution()">Hacky Solution</button>
  <svg width="960" height="600"></svg>
  <script src="https://cdnjs.cloudflare.com/ajax/libs/d3/4.2.3/d3.min.js"></script>
</body>
</html>

Answer 1

那是不是一个 hacky 解决方案！这是重新加热模拟的正确、惯用的方法。

这里的问题是当你做...

d3.selectAll("svg > *").remove()

...您只是删除了 DOM 元素。然而，模拟仍然是运行，并且已经冷却下来。

实际上，如果您等到模拟完全完成（大约 5 秒）再单击 "Clear and Redraw"，您会看到节点总是堆积起来在原点（左上角）。尝试点击它们：它们将移动到中心（因为拖动功能有点重新加热模拟，因为它有一个 alphaTarget）。

因此，您必须重新加热它。

但是，您应该使用 alpha:

，而不是使用 alphaTarget

simulation.alpha(0.8).restart()

这是进行了更改的代码：

var svg = d3.select("svg"),
    width = +svg.attr("width"),
    height = +svg.attr("height");

var color = d3.scaleOrdinal(d3.schemeCategory20);

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));

// I wrapped the d3.json invocation in this function
function drawGraph() {
  d3.json("https://gist.githubusercontent.com/mbostock/4062045/raw/5916d145c8c048a6e3086915a6be464467391c62/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")
        .attr("stroke-width", function(d) { return Math.sqrt(d.value); });

    var node = svg.append("g")
        .attr("class", "nodes")
      .selectAll("circle")
      .data(graph.nodes)
      .enter().append("circle")
        .attr("r", 5)
        .attr("fill", function(d) { return color(d.group); })
        .call(d3.drag()
            .on("start", dragstarted)
            .on("drag", dragged)
            .on("end", dragended));

    node.append("title")
        .text(function(d) { return d.id; });

    simulation
        .nodes(graph.nodes)
        .on("tick", ticked);

    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; });
    }
  });
}

// When I call it hear, all is well (as you would expect).
drawGraph()

// But when I clear and redraw it (by pressing a button), the nodes
// don't spread out.
function clearRedraw() {
  d3.selectAll("svg > *").remove()
  drawGraph()
}

function hackySolution() {
  d3.selectAll("svg > *").remove()
  drawGraph()
  simulation.alpha(0.8).restart()
}


function dragstarted(d) {
  if (!d3.event.active) simulation.alphaTarget(0.3).restart();
  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);
  d.fx = null;
  d.fy = null;
}

.links line {
  stroke: #999;
  stroke-opacity: 0.6;
}

.nodes circle {
  stroke: #fff;
  stroke-width: 1.5px;
}

<!DOCTYPE html>
<html>
<head>
  <meta charset="utf-8">
  <meta name="viewport" content="width=device-width">
  <title>JS Bin</title>
</head>
<body>
  <button onclick="clearRedraw()">Clear And Redraw</button>
  <button onclick="hackySolution()">Hacky Solution</button>
  <svg width="960" height="600"></svg>
  <script src="https://cdnjs.cloudflare.com/ajax/libs/d3/4.2.3/d3.min.js"></script>
</body>
</html>

或者，如果您仍然觉得重新加热模拟是一个 hacky 解决方案（事实并非如此），只需将模拟分配移动到 drawGraph 函数内部：

var svg = d3.select("svg"),
  width = +svg.attr("width"),
  height = +svg.attr("height");

var color = d3.scaleOrdinal(d3.schemeCategory20);



// I wrapped the d3.json invocation in this function
function drawGraph() {
  d3.json("https://gist.githubusercontent.com/mbostock/4062045/raw/5916d145c8c048a6e3086915a6be464467391c62/miserables.json", function(error, graph) {
    if (error) throw error;

    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));

    var link = svg.append("g")
      .attr("class", "links")
      .selectAll("line")
      .data(graph.links)
      .enter().append("line")
      .attr("stroke-width", function(d) {
        return Math.sqrt(d.value);
      });

    var node = svg.append("g")
      .attr("class", "nodes")
      .selectAll("circle")
      .data(graph.nodes)
      .enter().append("circle")
      .attr("r", 5)
      .attr("fill", function(d) {
        return color(d.group);
      })
      .call(d3.drag()
        .on("start", dragstarted)
        .on("drag", dragged)
        .on("end", dragended));

    node.append("title")
      .text(function(d) {
        return d.id;
      });

    simulation
      .nodes(graph.nodes)
      .on("tick", ticked);

    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;
        });
    }
  });
}

// When I call it hear, all is well (as you would expect).
drawGraph()

// But when I clear and redraw it (by pressing a button), the nodes
// don't spread out.
function clearRedraw() {
  d3.selectAll("svg > *").remove()
  drawGraph()
}


function dragstarted(d) {
  if (!d3.event.active) simulation.alphaTarget(0.3).restart();
  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);
  d.fx = null;
  d.fy = null;
}

.links line {
  stroke: #999;
  stroke-opacity: 0.6;
}

.nodes circle {
  stroke: #fff;
  stroke-width: 1.5px;
}

<button onclick="clearRedraw()">Clear And Redraw</button>
<svg width="960" height="600"></svg>
<script src="https://cdnjs.cloudflare.com/ajax/libs/d3/4.2.3/d3.min.js"></script>

动态插入的 d3 力图未展开

Dynamically inserted d3 force graph not spreading out

javascript

d3.js

svg

force-layout