D3 force-directed graph( v4) is not accepting img as nodes - d3.js

Question

I am trying to generate a force directed graph. I am able to achieve it if I use 'circle/rect' to draw nodes. But I want to use an image instead. What am I doing wrong?
Here is how I create and transform nodes (I am using d3 v4):
var node = svg.append("g")
.attr("class", "nodes f32")
.selectAll("img")
.data(json.nodes)
.enter().append("img")
.attr("class","flag ar")
.call(d3.drag()
.on("start", dragstarted)
.on("drag", dragged)
.on("end", dragended));
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
.style("left", function(d) { return d.x = Math.max(radius, Math.min(width - radius, d.x)); })
.style("top", function(d) { return d.y = Math.max(radius, Math.min(height - radius, d.y)); });
}
And here is a demo of what I have so far:
var svg = d3.select("svg"),
width = +svg.attr("width"),
height = +svg.attr("height"),
radius=5;
var simulation = d3.forceSimulation()
.force("link", d3.forceLink().id(function(d,index) { return d.id; }).distance(10))
.force("charge", d3.forceManyBody().distanceMin(10).distanceMax(120))
.force("center", d3.forceCenter(width / 2, height / 2));
d3.json("https://raw.githubusercontent.com/DealPete/forceDirected/master/countries.json",function(json ) {
json.nodes.forEach(function(d,i){
d.id = i;
})
var link = svg.append("g")
.attr("class", "links")
.selectAll("line")
.data(json.links)
.enter().append("line")
.attr("stroke-width","1");
var node = svg.append("g")
.attr("class", "nodes f32")
.selectAll("img")
.data(json.nodes)
.enter().append("img")
.attr("class","flag ar")
.call(d3.drag()
.on("start", dragstarted)
.on("drag", dragged)
.on("end", dragended));
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
.style("left", function(d) { return d.x = Math.max(radius, Math.min(width - radius, d.x)); })
.style("top", function(d) { return d.y = Math.max(radius, Math.min(height - radius, d.y)); });
}
simulation
.nodes(json.nodes)
.on("tick", ticked);
simulation.force("link")
.links(json.links);
});
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;
}
h1{
font-family: arial;
}
body{
display:flex;
justify-content:center;
align-items:center;
flex-direction: column;
background:#d64d4d;
}
.fdd{
width:1000px;
height:500px;
background: white;
}
<script src="https://d3js.org/d3.v4.min.js"></script>
<h1>Force Directed Graph of State Contiguity</h1>
<div class="fdd">
<svg width="1000" height="500"></svg>
</div>

Answer 1

To include an image element, you should use .append("image") instead of .append("img").
In addition, the image itself needs to be specified with the xlink:href attribute. You can provide a link to an image for instance.
These 2 points combined gives the following snippet:
.append("image")
.attr("class","flag ar")
.attr("xlink:href", "https://cdn.sstatic.net/Sites/stackoverflow/img/favicon.ico")
In addition, the location of nodes seems to be off; you can set their position this way (by translating them):
node.attr("transform", function(d) { return "translate(" + d.x + "," + d.y + ")"; })
Here is a demo:
var svg = d3.select("svg"),
width = +svg.attr("width"),
height = +svg.attr("height"),
radius=5;
var simulation = d3.forceSimulation()
.force("link", d3.forceLink().id(function(d,index) { return d.id; }).distance(10))
.force("charge", d3.forceManyBody().distanceMin(10).distanceMax(120))
.force("center", d3.forceCenter(width / 2, height / 2));
d3.json("https://raw.githubusercontent.com/DealPete/forceDirected/master/countries.json",function(json ) {
json.nodes.forEach(function(d,i){
d.id = i;
})
var link = svg.append("g")
.attr("class", "links")
.selectAll("line")
.data(json.links)
.enter().append("line")
.attr("stroke-width","1");
var node = svg.append("g")
.attr("class", "nodes f32")
.selectAll("image")
.data(json.nodes)
.enter().append("image")
.attr("class","flag ar")
.attr("xlink:href", "https://cdn.sstatic.net/Sites/stackoverflow/img/favicon.ico")
.attr("height", "32") // width/height (are necessary in Firefox to make the image appear)
.attr("width", "32")
.call(d3.drag()
.on("start", dragstarted)
.on("drag", dragged)
.on("end", dragended));
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; });
// -16 is half the width/height of the image I used:
node
.attr("transform", function(d) { return "translate(" + (d.x - 16) + "," + (d.y - 16) + ")"; })
}
simulation
.nodes(json.nodes)
.on("tick", ticked);
simulation.force("link")
.links(json.links);
});
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;
}
h1{
font-family: arial;
}
body{
display:flex;
justify-content:center;
align-items:center;
flex-direction: column;
background:#d64d4d;
}
.fdd{
width:1000px;
height:500px;
background: white;
}
<script src="https://d3js.org/d3.v4.min.js"></script>
<h1>Force Directed Graph of State Contiguity</h1>
<div class="fdd">
<svg width="1000" height="500"></svg>
</div>

Answer 2

I was confused between img and svg:image .
var svg = d3.select("svg"),
width = +svg.attr("width"),
height = +svg.attr("height"),
radius=5;
var graph = d3.select(".fdd")
.append("div")
.style("width", width + "px")
.style("height", height + "px")
.attr('class',"countries f16")
var node = graph
.selectAll("img")
.data(json.nodes)
.enter().append("img")
.attr("class",function(d){return "flag " +d.code} )
.call(d3.drag()
.on("start", dragstarted)
.on("drag", dragged)
.on("end", dragended))
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
.style("top", function(d) { return d.y + "px"; } )
.style("left", function(d) { return d.x + "px"; });
}
Having img inside svg wasn't working.
Complete solution can be found here:
var svg = d3.select("svg"),
width = +svg.attr("width"),
height = +svg.attr("height"),
radius=5;
var graph = d3.select(".fdd")
.append("div")
.style("width", width + "px")
.style("height", height + "px")
.attr('class',"countries f16")
var simulation = d3.forceSimulation()
.force("link", d3.forceLink().id(function(d,index) { return d.id; }).distance(10))
.force("charge", d3.forceManyBody().distanceMin(10).distanceMax(120))
.force("center", d3.forceCenter(width / 2, height / 2));
d3.json("https://raw.githubusercontent.com/DealPete/forceDirected/master/countries.json",function(json ) {
json.nodes.forEach(function(d,i){
d.id = i;
})
var link = svg.append("g")
.attr("class", "links")
.selectAll("line")
.data(json.links)
.enter().append("line")
.attr("stroke-width","1");
var node = graph
.selectAll("img")
.data(json.nodes)
.enter().append("img")
.attr("class",function(d){return "flag " +d.code} )
.call(d3.drag()
.on("start", dragstarted)
.on("drag", dragged)
.on("end", dragended))
.on("mouseover", function(data,a){
return tooltip
.style("visibility", "visible")
.attr('class', 'd3-tip')
.html("<div class='data'>"+data.country+"</div>")
.style("top", (event.pageY-10)+"px").style("left",(event.pageX+10)+"px");})
.on("mouseout", function(){
return tooltip.style("visibility", "hidden");});
var tooltip = d3.select("body")
.append("div")
.style("position", "absolute")
.style("z-index", "100000")
.style("visibility", "hidden")
.text("a simple tooltip");
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
.style("top", function(d) { return d.y + "px"; } )
.style("left", function(d) { return d.x + "px"; });
}
simulation
.nodes(json.nodes)
.on("tick", ticked);
simulation.force("link")
.links(json.links);
});
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;
}
svg{
position:absolute;
}
.countries{
width: 100%;
height:100%;
position: relative;
margin: 0 auto;
}
h1{
font-family: arial;
}
body{
display:flex;
justify-content:center;
align-items:center;
flex-direction: column;
background:#d64d4d;
}
.fdd{
width:1000px;
height:500px;
background: white;
}
.flag{
position:absolute;
border-radius: 50%;
border: 0;
transform: translate(-8px,-8px);
}
<script src="https://d3js.org/d3.v4.min.js"></script>
<link href="https://github.com/downloads/lafeber/world-flags-sprite/flags16.css" rel="stylesheet"/>
<h1>Force Directed Graph of State Contiguity</h1>
<div class="fdd">
<svg width="1000" height="500"></svg>
</div>