how to add title to d3js bubble chart with force layout - d3.js

Question

This is the code of the bubble chart i created. I have used force layout to create the chart.
var margin = {
top: 10,
right: 10,
bottom: 10,
left: 10
},
width = 1000 - margin.left - margin.right,
height = 600 - margin.top - margin.bottom;
d3.select('#' + divId).append('div').attr('id', 'chart').attr('class', 'chart');
var n = data.vistaJson.length;
m = 1,
padding = 5,
radius = d3.scale.sqrt().range([10, 50]),
color = d3.scale.category10().domain(d3.range(m)),
x = d3.scale.ordinal().domain(d3.range(m)).rangePoints([0, width], 1);
var xscale = d3.scale.linear()
.domain([0, 500])
.range([20, 500]);
var nodes = [];
for(var i=0; i< n; i++){
var coordinates = data.vistaJson[i].SLAB.split('_');
v = data.vistaJson[i].COUNT
nodes.push({
radius: radius(v),
color: color(i),
count: v,
cx: xscale(x(i)),
cy: xscale(height / 2),
xAxis: coordinates[0],
yAxis: coordinates[1]
});
}
var svg = d3.select("#chart").append("svg")
.attr("width", width + margin.left + margin.right)
.attr("height", height + margin.top + margin.bottom)
.append("g")
.attr("transform", "translate(" + margin.left + "," + margin.top + ")");
var force = d3.layout.force()
.nodes(nodes)
.size([width, height])
.gravity(0.5)
.charge(0.5)
.on("tick", tick)
.start();
var circle = svg.selectAll("circle")
.data(nodes)
.enter().append("circle")
.attr("r", function (d) {
return d.radius;
})
.style("fill", function (d) {
return d.color;
})
.call(force.drag);
var labels = svg.selectAll("text")
.data(nodes)
.enter()
.append("text")
.attr({"x":function(d){return d.x;},
"y":function(d){return d.y;}})
.text(function(d){return d.count;})
.call(force.drag);
circle.each(gravity(.2 * e.alpha))
.each(collide(.5))
.attr("cx", function (d) {
return d.x;
})
.attr("cy", function (d) {
return d.y;
});
labels.attr("x", function(d) { return d.x; })
.attr("y", function(d) { return d.y; });
}
// Move nodes toward cluster focus.
function gravity(alpha) {
return function (d) {
d.y += (d.cy - d.y) * alpha;
d.x += (d.cx - d.x) * alpha;
};
}
// Resolve collisions between nodes.
function collide(alpha) {
var quadtree = d3.geom.quadtree(nodes);
return function (d) {
var r = d.radius + radius.domain()[1] + padding,
nx1 = d.x - r,
nx2 = d.x + r,
ny1 = d.y - r,
ny2 = d.y + r;
quadtree.visit(function (quad, x1, y1, x2, y2) {
if (quad.point && (quad.point !== d)) {
var x = d.x - quad.point.x,
y = d.y - quad.point.y,
l = Math.sqrt(x * x + y * y),
r = d.radius + quad.point.radius + (d.color !== quad.point.color) * padding;
if (l < r) {
l = (l - r) / l * alpha;
d.x -= x *= l;
d.y -= y *= l;
quad.point.x += x;
quad.point.y += y;
}
}
return x1 > nx2 || x2 < nx1 || y1 > ny2 || y2 < ny1;
});
};
}
I want to add title to the node which is displayed when mouse is hovered on the node .
Earlier I used pack layout and I gave title like this :
var node = vis.selectAll("g.node")
.data(bubble.nodes(classes(json), function(d) { return d.name; })
.filter(function(d) { return !d.children; }))
.enter()
.append("svg:g")
.attr("class", "node")
.attr("transform", function(d) { return "translate(" + xscale(d.x) + "," + xscale(d.y) + ")"; });
node.append("svg:title")
.text(function(d) { return d.xAxis + ": " + d.yAxis; });
How can we show title when using forceLayout . Please help .

Answer 1

I think it should look something like this in the force layout:
var node = svg.selectAll(".node")
.data(graph.nodes)
.enter().append("circle")
.attr("class", function(d) { return d.nodes ? "nonleaf" : "leaf"; })
.attr("r", 5)
.call(force.drag);
node.append("title")
.text(function(d) { return d.count; });
I hope this helps somehow. For me it works like that..