user3766479 user3766479 - 5 months ago 42
Javascript Question

I want to add text on the link in D3.js tree graph

I want to make a decision tree in D3.js and to add text on the link.

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

<body><script src="../d3-master/d3.min.js"></script>
<head><link rel="stylesheet" type="text/css" href="../D3css/D3css.css"></head>

<script>

var margin = {top: 20, right: 20, bottom: 30, left: 40},
width = 960 - margin.left - margin.right,
height = 500 - margin.top - margin.bottom,
rect_width = 90,
rect_height = 20;

var tree = d3.layout.tree()
.size([height * 2, width / 2]);

var diagonal = d3.svg.diagonal()
.projection(function(d) { return [d.x, d.y]; });

var svg = d3.select("body").append("svg")
.attr("width", width + margin.left + margin.right)
.attr("height", height + margin.top + margin.bottom)
.append("g")
.attr("transform", "translate(" + margin.left + "," + margin.top + ")");

d3.json("../data/ID3.json", function(error, root) {

var nodes = tree.nodes(root),
links = tree.links(nodes);

var link = svg.selectAll(".link")
.data(links)
.enter().append("g")
.attr("calss", "link")
.attr("fill", "none");

link.append("path")
.attr("d", diagonal)
.attr("stroke", "lightsteelblue");

link.append("text")
.data(nodes)
.attr("transform", function(d) { return "translate(" + d.x + "," + d.y + ")"; })
.attr("y", -85)
.attr("text-anchor", "middle")
.attr("fill", "black")
.text(function(d) { return d.rule; });

var node = svg.selectAll(".node")
.data(nodes)
.enter().append("g")
.attr("class", "node")
.attr("transform", function(d) { return "translate(" + d.x + "," + d.y + ")"; });

node.append("rect")
.attr("transform", "translate(-42,-8)")
.attr("width", rect_width)
.attr("height", rect_height)
.style("fill", "lightsteelblue");

node.append("text")
.attr("dy", ".31em")
.attr("text-anchor", "middle")
.attr("transform", function(d) { return "translate(" + d.x / 128 + "," + d.y / 128 + ")"; })
.text(function(d) { return d.name; });

});

</script>


There is no text on the link at the bottom right.
I think to was due to use 'nodes' data.
so, I tried in to use 'root' data.
but, I don't come out of nothing if I use 'root' data.

I think that this part is problem.

link.append("text")
.data(nodes)

How should I revise??

my data.

{ "name" : "0", "rule" : "null",
"children" : [{ "name" : "2", "rule" : "sunny",
"children" : [{ "name" : "no(3/100%)", "rule" : "high" },
{ "name" : "yes(2/100%)", "rule" : "normal" }]},
{ "name" : "yes(4/100%)", "rule" : "overcast" },
{ "name" : "3", "rule" : "rainy",
"children" : [{ "name" : "no(2/100%)", "rule" : "TRUE" },
{ "name" : "yes(3/100%)", "rule" : "FALSE" }]}]}

Answer

For links, one can't access d.x, d.y, d.rule, or similar fields, since link is not associated with a single data point, but it has its source and target. This means the data should be accessed like this: d.source.x, d.target.y, and so on.

The key code segment should look like this:

var link = svg.selectAll(".link")
    .data(links)
    .enter()
    .append("g")
    .attr("class", "link");

link.append("path")
    .attr("fill", "none")
    .attr("stroke", "#ff8888")
    .attr("stroke-width", "1.5px")
    .attr("d", diagonal);

link.append("text")
    .attr("font-family", "Arial, Helvetica, sans-serif")
    .attr("fill", "Black")
    .style("font", "normal 12px Arial")
    .attr("transform", function(d) {
        return "translate(" +
            ((d.source.y + d.target.y)/2) + "," + 
            ((d.source.x + d.target.x)/2) + ")";
    })   
    .attr("dy", ".35em")
    .attr("text-anchor", "middle")
    .text(function(d) {
        console.log(d.target.rule);
         return d.target.rule;
    });

Here is working example: jsfiddle

enter image description here

Of course, you can change text color, position, etc. to suit your needs.

Hope this helps.

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