D3 force layout fix root node at the center

Question

I managed to draw some basic d3 force layout graph, but struggling how to fix root node at the center.

My data is rather simple; one root node with one-level children. Only one level. Another particular thing about my graph is that the link distance varies based on some parameter.

I want root node to be at the center of the graph.

Setting its property 'fixed':true doesn't work. Any idea to place root node at the center?

Solution

force.on("tick", function() {
    nodes[0].x = w / 2;
    nodes[0].y = h / 2;

That should do it.

Comments

[FernOfTheAndes]

Example here. Look inside force.on at the first two lines.

[samuelg0rd0n]

Is it possible to alter the behaviour in a way that the node is initially centered but the user can still move it?

[bryanph]

In d3 4.0 this doesn't fix nodes but just sets the coordinates. To fix the node use "fx" and "fy"