从动态 json 数据更新力有向图上的链接

I am new to D3 and working on a force directed graph where the json data is dynamic. I am able to change the force graph upon receiving new data but that happens with a springing effect. The code that creates my force graph is :

<div class="graph"></div>
<script>
var w = 660,
    h = 700,
    r = 10;
var vis = d3.select(".graph")
    .append("svg:svg")
    .attr("width", w)
    .attr("height", h)
    .attr("pointer-events", "all")
    .append('svg:g')
    .call(d3.behavior.zoom().on("zoom", redraw))
    .append('svg:g');
vis.append('svg:rect')
    .attr('width', w)
    .attr('height', h)
    .attr('fill', 'rgba(1,1,1,0)');
function redraw() {
    console.log("here", d3.event.translate, d3.event.scale);
    vis.attr("transform", "translate(" + d3.event.translate + ")" +
                          " scale(" + d3.event.scale + ")");
};  

var force = d3.layout.force()
    .gravity(.05)
    .charge(-200)
    .linkDistance( 260 )
    .size([w, h]);

var svg = d3.select(".text")
    .append("svg")
    .attr("width", w)
    .attr("height", h);

d3.json(graph, function(json) {

    var nodeList = json.nodes;
    var link = vis.selectAll("line")
        .data(json.links)
       .enter()
        .append("line")
        .attr("stroke-opacity", function(d) {
            if(d.label == 'is a') {
                return '0.8';
            } else {
                return '0.2';
            };
        })
        .attr("stroke-width", function(d) {
            if(d.value !== null) {
                return d.value;
            } else {
                return 2;
            };
        })
        .style("stroke", function(d) {
            if(d.color !== null) {
                return d.color;
            };
        })
        .on("mouseover", function() {
            d3.select(this)
                .style("stroke", "#999999")
                .attr("stroke-opacity", "1.0");
        })
        .on("mouseout", function() {
            d3.select(this)
                .style("stroke", function(d) {
                    if(d.color !== null) {
                        return d.color;
                    };
                })
                .attr("stroke-opacity", function(d) {
                    if(d.label == 'is a') {
                        return '0.8';
                    } else {
                        return '0.2';
                    };
                })
            });

    link.append("title")
        .text(function(d) { return d.label } );         

    var node = vis.selectAll("g.node")
        .data(json.nodes)
       .enter()
        .append("svg:g")
        .attr("class","node")
        .call(force.drag);

    node.append("svg:circle")
        .attr("r", function(d) {
            if (d.size > 0) {
                return 10+(d.size*2);
            } else {
                return 10;
            }
        })
        .attr("id", function(d) { return "Node;"+d.id; } )
        .style("fill", function(d) {
            if(d.style == 'filled') {
               return d.color;
            };
        })
        .style("stroke", function(d) {
            if(d.style !== 'filled') {
                return d.color;
            };
        })
        .style("stroke-width", "2")
        .on("mouseover", function() {
            d3.select(this).style("fill", "#999");
            fade(.1);
        })
        .on("mouseout", function(d) {
            if (d.style == 'filled') {
                d3.select(this).style("fill",d.color);fade(1);
            } else {
                d3.select(this).style("stroke",d.color);
                d3.select(this).style("fill","black");
            }
            fade(1);
        });

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

    force.nodes(json.nodes)
        .links(json.links)
        .on("tick", tick)
        .alpha(1)
        .start();

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

    link.attr("x1", function(d) { return d.source.x; })
        .attr("y1", function(d) { return d.source.y; })
        .attr("x2", function(d) { return d.target.x; })
        .attr("y2", function(d) { return d.target.y; });
    }

});
</script>

当收到新的json字符串时，我可以通过再次调用整个函数来创建新的图形.这将在旧图形的位置创建一个新图形.当接收到值时，我无法用新的值集更新旧图；我的图中的 node 没有改变，只是它们之间的关系改变了.

我确实偶然发现了一个示例(http://bl.ocks.org/1095795)，其中删除并重新创建了一个新 node ，但实现有点不同.

Any pointers or help will be really appreciated.