force multiple centers

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<!DOCTYPE html>
<meta charset="utf-8">
<style>

.links line {
  stroke: #999;
  stroke-opacity: 0.6;
}

.nodes circle {
  stroke: #fff;
  stroke-width: 1.5px;
}

</style>
<svg width="960" height="600"></svg>
<script src="https://d3js.org/d3.v4.min.js"></script>
<script>

var svg = d3.select("svg"),
    width = +svg.attr("width"),
    height = +svg.attr("height");

var color = d3.scaleOrdinal(d3.schemeCategory10);

var nodes = d3.range(100).map(function() {
   var node = {};
   node.groupA = Math.floor(Math.random()*5);
   node.groupB = Math.floor(Math.random()*3);
   return node;
})

var fociA = [{x:200,y:250},{x:350,y:250},{x:500,y:250},{x:650,y:250},{x:800,y:250}]
var fociB = [{x:400,y:100},{x:600,y:300}, {x: 100, y: 100}];

var simulation = d3.forceSimulation()
    .force("link", d3.forceLink().id(function(d) { return d.id; }))
    .force("charge", d3.forceManyBody())
    .force("center", d3.forceCenter(width / 2, height / 2));

var node = svg.append("g")
    .attr("class", "nodes")
    .selectAll("circle")
    .data(nodes)
    .enter().append("circle")
      .attr("r", 5)
      .attr("fill", function(d) { return color(d.groupA); })
      .call(d3.drag()
          .on("start", dragstarted)
          .on("drag", dragged)
          .on("end", dragended));

node.append("title")
      .text(function(d) { return d.id; });

simulation
      .nodes(nodes)
      .on("tick", ticked);
  
	  
var current = "groupA";
var buttons = svg.selectAll(null)
  .data(["groupA","groupB"])
  .enter()
  .append("g")
  .attr("transform",function(d,i)  { return "translate("+(i*120+50)+","+50+")"; })
  .on("click", function(d) {
    if(d != current) {
	      current = d;
		  simulation.alpha(0.228);
		  simulation.restart();
	  } 
  })
  .style("cursor","pointer")
  
buttons.append("rect")
  .attr("width",100)
  .attr("height",50)
  .attr("fill","lightgrey")
    
buttons.append("text")
  .text(function(d) { return d; })
  .attr("dy", 30)
  .attr("dx", 50)
  .style("text-anchor","middle");

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

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;
}

</script>

https://d3js.org/d3.v4.min.js