Make the svg follow a hierarchical structure - svg

Question

I'm new with d3 and I was wondering if it is possible to make the svg follow the hierarchical structure of a tree.
Let's say that I have a json like that :
{
"name": "root",
"children": [
{
"name" : "child1",
"children": [
{
"name": "child1_1"
},
{
"name": "child1_2"
}
]
},
{
"name": "child2",
"children": [
{
"name": "child2_1"
},
{
"name": "child2_2"
}
]
}
]
}
How can I have a svg structure like this :
<g class="root">
<g class="child1">
<g class="child1_1">
</g>
<g class="child1_2">
</g>
</g>
<g class="child2">
<g class="child2_1">
</g>
<g class="child2_2">
</g>
</g>
</g>
I've tried stuff like that :
var w = 960,
h = 2000,
i = 0,
root;
var diagonal = d3.svg.diagonal()
.projection(function(d) { return [d.y, d.x]; });
var vis = d3.select("#chart").append("svg:svg")
.attr("width", w)
.attr("height", h)
.append("svg:g")
.attr("transform", "translate(40,0)");
d3.json(
'./small_tree.json',
function(json) {
json.x0 = 800;
json.y0 = 0;
update(root = json);
}
);
function update(source) {
var nodes = tree.nodes(root);
var child = vis.selectAll('g.child_node')
.data(nodes,function(d){return d.children;})
.enter()
.append('g')
.attr("class", "child_node");
}
And I'm getting a tag for the children of the root node, but I don't know how to recursively create nested group for children of children.
Anyone have an idea ?
Thanks,
Rem

Answer 1

D3 doesn't natively handle recursion, and it looks like the standard hierarchical layouts don't, in general, create nested structures. Instead, you need to recurse in your own code. Here's one implementation:
// simple offset, just to make things visible
var offset = 0;
// recursion function
function addNode(selection, depth) {
// set the current children as the data array
var nodeGroup = selection.selectAll('g.child_node')
.data(function(d) { return d.children })
.enter()
// add a node for each child
.append('g')
.attr("class", "child_node")
// very simple depth-based placement
.attr("transform", "translate(" + (depth * 30) + "," +
(++offset * 15) + ")");
nodeGroup.append("text")
.attr("dy", "1em")
.text(function(d) { return d.name });
// recurse - there might be a way to ditch the conditional here
nodeGroup.each(function(d) {
if (d.children) nodeGroup.call(addNode, depth + 1);
});
}
d3.json(
'./small_tree.json',
function(root) {
// kick off the recursive append
vis
.datum({ children: [root] })
.call(addNode, 0);
}
}
See fiddle: http://jsfiddle.net/nrabinowitz/ELYWa/