大数据集打破 d3 桑基图

Question

I'm making a d3 Sankey diagram from the example in https://bl.ocks.org/d3noob/5028304 . This example works fine with a smaller data set. When I switched to using a larger data set, the visualization breaks. It looks like the problem is that the dy values become negative.

In the console, the error is:

Error: <rect> attribute height: A negative value is not valid. ("-9.02557856272838")

The code it points to is:

node.append("rect")
  .attr("height", function(d) { return d.dy; })

This is perhaps because the plots are going off screen? I looked at using d3 scales, but I'm not sure how to implement them. Maybe something like this:

d3.scale.ordinal()
.domain(data.map(function(d) { return d.name; }))
.rangeRoundBands([0, height], .2);

Or maybe there's a way to shrink the visualization as the data set gets larger so that everything will fit in the container.

Here is my code: https://plnkr.co/edit/hOjEBHhS7vfajD2wb8t9?p=preview

Answer 1

With 945 nodes and 2463 links, there is no way this is going to fit in an 740-pixel-height container. Not only that, you have to ask yourself "how is this dataviz going to be useful to the reader with that huge amount of information?" . But since that's none of my business, you can do a couple of things:

The first one, of course, is filtering your data. If that's not an option, you can increase the container height:

height = 3000 - margin.top - margin.bottom;

And reduce the padding of the nodes:

var sankey = d3.sankey()
    .nodeWidth(36)
    .nodePadding(1)
    .size([width, height]);

The result is in this plunker: https://plnkr.co/edit/Idb6ZROhq1kuZatbGtqg?p=preview

But if even that is not an option, you can change sankey.js code or, in a lazy solution, avoid negative numbers with this:

.attr("height", function(d) { return d.dy < 0 ? 0 : d.y; })

This being the result: https://plnkr.co/edit/tpaMpK5yXwYh9MEo8hgn?p=preview

Answer 2

I've encountered the same problem. I have graphs with 50 nodes and 50 links, but also graphs with 1200 nodes and 1200 links. The first thing I tried was to increase the canvas width and height. So I've increased the width based on the graph depth and the height based on the level where I had the most nodes.

However, I ended up in some edge cases graphs with either a too bigger width or too bigger height. So I ended up with a regeneration of the graph, until each node has a min height and until the space between the linked nodes is reasonable.

So here is what I did:

class SankeyChart {
   sankeyGenerator;
   graph;
   width = 1000;
   height = 1000;

   constructor(private nodes, private links) {
      this.sankeyGenerator = sankey()
        .extent([[10, 10], [this.width - 10, this.height - 10]])
      this.draw();
   }

 
  private draw() {
    this.graph = this.getGraph();
    this.drawLinks(this.graph.links); // method that draw the links
    this.drawNodes(this.graph.nodes); // method that draw the nodes
  }


  private getGraph() {
    const graph = this.sankeyGenerator({nodes: this.nodes, links: this.links});

    const increaseWidth = graph.links.some(l => Math.abs(l.source.y1 - l.target.y0) > 4 * Math.abs(l.source.x1 - l.target.x0));
    const increaseHeight = graph.nodes.some(n => n.y1 - n.y0 < 1);
    if (increaseHeight) {
      this.height += 1000;
    }
    if (increaseWidth) {
      this.width += 1000;
    }
    if (increaseHeight || increaseWidth) {
      this.sankeyGenerator.extent([[10, 10], [this.width - 10, this.height - 10]]);
      return this.getGraph();
    }
    return graph;
  }

}

Note that you might want to perform an extra filter on graph.nodes.some(n => n.y1 - n.y0 < 1); . I had a few cases where all the nodes had y1 - y0 > 1000 , but there were 2 or 3 nodes where y1 - y0 < 0.00000001 .

Also note that you might add a parameter to the class to increase the size of the container more than 1000px each time when getGraph() is called for big charts.