Change orientation of Arrow Marker in D3 oriented force graph

Question

I'm trying to insert an arrow marker in each one of my links. But I would like to change the orientation of the arrows, make them face the other end of each link.

Here's the code:

    svg.append("svg:defs").selectAll("marker")
        .data(["end"])      // Different link/path types can be defined here
      .enter().append("svg:marker")
        .attr("id", "end")    // This section adds in the arrows
        .attr("viewBox", "0 -5 10 10")
        .attr("refX", 15)
        .attr("refY", -1.5)
        .attr("markerWidth", 6)
        .attr("markerHeight", 6)
        .attr("orient", 180)
      .append("svg:path")
        .attr("d", "M0,-5L10,0L0,5");

    // add the links and the arrows
    var pg = svg.append("svg:g").selectAll("path")
        .data(force.links())
      .enter().append("g");

    var path = pg.append("path")
        .attr("class", "link")
        .attr("marker-end", "url(#end)")

how is that possible?

I've tried to change .attr("marker-end", "url(#end)");

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

but then the markers just dissapear. One more thing I would like to know is what part of the code defines the curvature of the links and how to change that.

Thank you.

score 4 · Answer 1 · edited May 23 '17 at 12:16

4

You should look at the "orient" attribute of markers: https://www.w3.org/TR/svg-markers/#OrientAttribute

in your case something like: .attr("orient", "auto-start-reverse") or .attr("orient", 180) would work.

An example can be found at this post: Display an arrow head in the middle of D3 force layout link

As for the curvature, the related part is

dr = Math.sqrt(dx * dx + dy * dy);

as dr, the radius, gets bigger there will be more curve.

edited May 23 '17 at 12:16

Community

1
1

answered May 11 '16 at 11:22

eko

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The .attr("orient", "auto-start-reverse") made no effect ): – Lucas Azevedo May 11 '16 at 11:40
It actually works, but only with `.attr("marker-start", "url(#end)")`. When I try `.attr("marker-mid", "url(#end)")` it dissapears ): – Lucas Azevedo May 11 '16 at 11:47
I've inserted my code into the original post. Would you try it in your environment to see if it works? Thanks – Lucas Azevedo May 11 '16 at 12:26
why there are so many appends? `var path = svg.append("svg:g").selectAll("path") .data(force.links()) .enter().append("svg:path")` – Lucas Azevedo May 11 '16 at 12:39
Even if I delete the pg and the text and paste your code, the arrows doesn't appear. – Lucas Azevedo May 11 '16 at 12:47
@LucasLourenço I think you are missing the calculation of the mid point in the tick event. Are you defining your midpoint? – eko May 11 '16 at 12:56
No. Im just using `"marker-mid"` Do I have to define it? When I use `.attr("orient", "auto")` and `"marker-mid"` it works... – Lucas Azevedo May 11 '16 at 13:56
Well, I've managed by changing the `.attr("refX",80)` on the markers. – Lucas Azevedo May 11 '16 at 14:19

score 0 · Answer 2 · answered May 11 '16 at 11:23

svg.select("defs").append("marker")
    .attr("id", "start")
    .attr("viewBox", "0 -5 10 10")
    .attr("refX", -5)
    .attr("refY", 0)
    .attr("markerWidth", 6)
    .attr("markerHeight", 6)    
    .attr("orient", "auto")
    .append("path")
    .attr("d", "M0,0L10,-5L10,5");

var path = svg.append("svg:g").selectAll("path")
    .data(force.links())
    .enter().append("svg:path")
    .attr("class", "link")
    .attr("marker-start", "url(#start)")
    .attr("marker-end", "url(#end)");

var links= [
  {
    "source": "Harry",
    "target": "Sally",
    "value": 1.2
  },
  {
    "source": "Harry",
    "target": "Mario",
    "value": 1.3
  },
  {
    "source": "Sarah",
    "target": "Alice",
    "value": 0.2
  },
  {
    "source": "Eveie",
    "target": "Alice",
    "value": 0.5
  },
  {
    "source": "Peter",
    "target": "Alice",
    "value": 1.6
  },
  {
    "source": "Mario",
    "target": "Alice",
    "value": 0.4
  },
  {
    "source": "James",
    "target": "Alice",
    "value": 0.6
  },
  {
    "source": "Harry",
    "target": "Carol",
    "value": 0.7
  },
  {
    "source": "Harry",
    "target": "Nicky",
    "value": 0.8
  },
  {
    "source": "Bobby",
    "target": "Frank",
    "value": 0.8
  },
  {
    "source": "Alice",
    "target": "Mario",
    "value": 0.7
  },
  {
    "source": "Harry",
    "target": "Lynne",
    "value": 0.5
  },
  {
    "source": "Sarah",
    "target": "James",
    "value": 1.9
  },
  {
    "source": "Roger",
    "target": "James",
    "value": 1.1
  },
  {
    "source": "Maddy",
    "target": "James",
    "value": 0.3
  },
  {
    "source": "Sonny",
    "target": "Roger",
    "value": 0.5
  },
  {
    "source": "James",
    "target": "Roger",
    "value": 1.5
  },
  {
    "source": "Alice",
    "target": "Peter",
    "value": 1.1
  },
  {
    "source": "Johan",
    "target": "Peter",
    "value": 1.6
  },
  {
    "source": "Alice",
    "target": "Eveie",
    "value": 0.5
  },
  {
    "source": "Harry",
    "target": "Eveie",
    "value": 0.1
  }
];

var nodes = {};

// 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});
    link.value = +link.value;
});

var width = 960,
    height = 500;

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

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

// build the arrow.
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");

svg.select("defs").append("marker")
    .attr("id", "start")
    .attr("viewBox", "0 -5 10 10")
    .attr("refX", -5)
    .attr("refY", 0)
    .attr("markerWidth", 6)
    .attr("markerHeight", 6)    
    .attr("orient", "auto")
    .append("path")
    .attr("d", "M0,0L10,-5L10,5");

// add the links and the arrows
var path = svg.append("svg:g").selectAll("path")
    .data(force.links())
    .enter().append("svg:path")
    .attr("class", "link")
    .attr("marker-start", "url(#start)")
    .attr("marker-end", "url(#end)");

// define the nodes
var node = svg.selectAll(".node")
    .data(force.nodes())
  .enter().append("g")
    .attr("class", "node")
    .call(force.drag);

// add the nodes
node.append("circle")
    .attr("r", 5);

// add the text 
node.append("text")
    .attr("x", 12)
    .attr("dy", ".35em")
    .text(function(d) { return d.name; });

// add the curvy lines
function tick() {
    path.attr("d", function(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;
    });

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

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

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

text {
  fill: #000;
  font: 10px sans-serif;
  pointer-events: none;
}

<script src="https://cdnjs.cloudflare.com/ajax/libs/d3/3.4.11/d3.min.js"></script>

Change orientation of Arrow Marker in D3 oriented force graph

2 Answers2