score:19

Accepted answer

I've found the answer in this post

var circle = svg.selectAll("circle")
    .data(data);

circle.enter().append("circle")
    .attr("r", 2.5);

circle
    .attr("cx", function(d) { return d.x; })
    .attr("cy", function(d) { return d.y; });

circle.exit().remove();

The answer is that I need to call attr operator on the result of selectAll.data and not on the result of the append operator.

score:4

There is an example at http://bl.ocks.org/1095795 that shows adding and removing nodes from a force directed layout. The links and nodes have to be handled separately and then the force layout has to be restarted.

function restart() {
  var link = vis.selectAll("line.link")
      .data(links, function(d) { return d.source.id + "-" + d.target.id; });

  link.enter().insert("svg:line", "g.node")
      .attr("class", "link");

  link.exit().remove();

  var node = vis.selectAll("g.node")
      .data(nodes, function(d) { return d.id;});

  var nodeEnter = node.enter().append("svg:g")
      .attr("class", "node")
      .call(force.drag);

  nodeEnter.append("svg:image")
      .attr("class", "circle")
      .attr("xlink:href", "https://d3nwyuy0nl342s.cloudfront.net/images/icons/public.png")
      .attr("x", "-8px")
      .attr("y", "-8px")
      .attr("width", "16px")
      .attr("height", "16px");

  nodeEnter.append("svg:text")
      .attr("class", "nodetext")
      .attr("dx", 12)
      .attr("dy", ".35em")
      .text(function(d) { return d.id });

  node.exit().remove();

  force.start();
}

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