Force Network Graph Selection

HTML

<select id = "opts">
  <option value="A" selected="selected">Set A</option>
  <option value="B" >Set B</option> 
</select>

JavaScript

var A =
{
  "nodes": [
    { "id": 0,"name": "One", "x": 125,"y": 150, "fixed": "false"},
    { "id": 1, "name": "Two","x": 215, "y": 25, "fixed": "false"},
    { "id": 2, "name": "Three","x": 325, "y": 100, "fixed": "false"}
    ],
  "edges":[
      {"source":0,"target":1,"value":"edge-A-One"},
      {"source":1,"target":2,"value":"edge-A-Two"}
]}
var B =
{
  "nodes": [
    { "id": 0,"name": "One", "x": 200,"y": 40, "fixed": "true"},
    { "id": 1, "name": "Two","x": 115, "y": 125, "fixed": "true"}
    ],
  "edges":[
      {"source":0,"target":1,"value":"Edge-B-One"}
]}

var w = 1200;
var h = 1000;

var svg;

function dblclick(d) {
    d3.select(this).classed("fixed", d.fixed = false);
    }
function dragstart(d) {
        d3.select(this).classed("fixed", d.fixed = true);
    }

function drawFN (dataset) {
	      var force = d3.layout.force()
                      .nodes(dataset.nodes)  
                      .links(dataset.edges)
                      .gravity(.05)
                      .charge(-180)
                      .linkDistance(200)
                      .size([w, h])
                      .start();
        svg = d3.select("body").append("svg")
            .attr("width", w)
            .attr("height", h);
    
        var drag = force.drag()
                        .on("dragstart", dragstart);

        var edges = svg.selectAll("line")
                       .data(dataset.edges, function(d) {return d.value;})  
        edges.enter()
             .append("line")
             .attr("stroke", "#808080")
             .attr("stroke-width", 2)
             .attr("marker-end", "url(#end)");  

        var nodes = svg.selectAll("g.node")
                        .data(dataset.nodes, function(d) {return d.name;})   
        nodes.enter()
             .append("g");
             
        nodes.attr("class", "node")
             .on("dblclick", dblclick)
             .call(drag);
        
        nodes.append("circle")
             .attr("r", 6) 
            ...