I am relatively new to d3 and have limited experience with web frontend development. In my current web application project, I am attempting to create a force directed graph. Despite spending several hours trying to make it work, I have been unable to display the links between nodes. I've compared my code to various examples online, but it still doesn't seem to be working. I'm not sure why the edges are not being drawn.
After logging the nodes and links to the console, I noticed that the nodes have additional attributes as mentioned in the d3 documentation, but the links do not. Below is my JavaScript file and the JSON data. I have simplified the JSON data to just three entries in an attempt to troubleshoot the issue.
var height = 1080;
var width = 1920;
var color = d3.scale.category20();
var force = d3.layout.force()
.linkDistance(-120)
.linkStrength(30)
.size([width, height]);
var svg = d3.select("body").append("svg")
.attr("width", width)
.attr("height", height);
d3.json("/static/javascript/language_data.json", function(data){
force
.nodes(data.languages)
.links(data.language_pairs)
.start();
var link = svg.selectAll(".link")
.data(data.language_pairs)
.enter().append("line")
.attr("class", "link");
var node = svg.selectAll(".node")
.data(data.languages)
.enter().append("circle")
.attr("class", "node")
.attr("r", 5)
.style("fill", function(d) { return color(d.group); })
.call(force.drag);
node.append("title")
.text(function(d) { return d.language; });
force.on("tick", function() {
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; });
});
});
Here is the JSON data:
Based on some examples I have seen, I believe that the source and target values represent index positions from the list of nodes.
{
"languages":[
{"language": "TypeScript", "group": 1},
{"language": "Java", "group": 2},
{"language": "VHDL", "group": 3}
],
"language_pairs":[
{"source": "0", "target": "1", "value": 5},
{"source": "1", "target": "2", "value": 5},
{"source": "2", "target": "0", "value": 5}
]
}
If I missed any important details, please let me know! Thank you for any assistance!