Learn D3.js

Fixing nodes to a position

Dragging the node to a position doesn't keep it there forever, since the simulation is still running and its x and y coordinates are still being modified. But you can override that behavior by setting the final coordinates in the fx and fy properties (fixed coordinates) instead of x and y (see Force/Interactive/3-drag-fix.html):

d3.drag().on('drag', function(d) {        d.fx = d3.event.x;        d.fy = d3.event.y;        console.log(sim.alpha())})

If any of fx or fy properties is present in a node, the simulation will copy their values to x and y, ignoring vx and vy. Now if you drag a node, it remains in its final position and no longer is affected by the rest of the simulation. You can then move all nodes to any position you wish. ...