Develop Reference

D3Js v3: Path not showing up on Node Elements

With Javascript Im generating HTML-Code with a SVG in it. I want to display a a donut chart in it then. Im able to draw the chart on a static HTML-Element. However, when I try to display it in my JavaScript-generated node element the path is not showing up, but I can see the text. What am I missing here?
https://jsfiddle.net/fuL5doja/46/
function createNodes(){
var parent = document.getElementById('chart');
var child = document.createElement('div');
child.classList.add('childContainer');
parent.appendChild(child);
var svg = document.createElement('svg');
svg.id = 'donut';
child.appendChild(svg);
}
function donutChart(){
// set the dimensions and margins of the graph
var width = 30
height = 30
margin = 0
// The radius of the pieplot is half the width or half the height (smallest one). I subtract a bit of margin.
var radius = 30
// append the svg object to the div called 'my_dataviz'
var svg = d3.select('#donut')
.attr("width", width)
.attr("height", height)
.append("g")
.attr("transform", "translate(" + width / 2 + "," + height / 2 + ")");
// Create dummy data
var dataDummy = {a: 70, b:30}
// set the color scale
var color = d3.scale.ordinal()
.domain(dataDummy)
.range(["#bebfc2", "#8FB91C"])
// Compute the position of each group on the pie:
var pie = d3.layout.pie()
.value(function(d) {return d.value; })
var data_ready = pie(d3.entries(dataDummy))
// Build the pie chart: Basically, each part of the pie is a path that we build using the arc function.
svg.selectAll('whatever')
.data(data_ready)
.enter()
.append('path')
.attr('d', d3.svg.arc()
.innerRadius(5) // This is the size of the donut hole
.outerRadius(radius)
)
.attr('fill', function(d){ return(color(d.data.key)) })
.style("opacity", 0.7)
svg.append("text")
.attr("x", -12) // space legend
.attr("y", 2)
.attr("class", "donutText")
.text('30%');
}
function donutChart2(){
// set the dimensions and margins of the graph
var width = 30
height = 30
margin = 0
// The radius of the pieplot is half the width or half the height (smallest one). I subtract a bit of margin.
var radius = 30
// append the svg object to the div called 'my_dataviz'
var svg = d3.select('#test')
.attr("width", width)
.attr("height", height)
.append("g")
.attr("transform", "translate(" + width / 2 + "," + height / 2 + ")");
// Create dummy data
var dataDummy = {a: 70, b:30}
// set the color scale
var color = d3.scale.ordinal()
.domain(dataDummy)
.range(["#bebfc2", "#8FB91C"])
// Compute the position of each group on the pie:
var pie = d3.layout.pie()
.value(function(d) {return d.value; })
var data_ready = pie(d3.entries(dataDummy))
// Build the pie chart: Basically, each part of the pie is a path that we build using the arc function.
svg.selectAll('whatever')
.data(data_ready)
.enter()
.append('path')
.attr('d', d3.svg.arc()
.innerRadius(5) // This is the size of the donut hole
.outerRadius(radius)
)
.attr('fill', function(d){ return(color(d.data.key)) })
.style("opacity", 0.7)
svg.append("text")
.attr("x", -12) // space legend
.attr("y", 2)
.attr("class", "donutText")
.text('30%');
}
createNodes();
donutChart();
donutChart2();
.childContainer {
width: 200px;
height: 100px;
border: 1px solid black;
}
#mySvg {
}
<div id="chart"></div>
<svg id="test"></svg>
<script src="https://cdnjs.cloudflare.com/ajax/libs/d3/3.5.17/d3.min.js"></script>
<script src="https://cdnjs.cloudflare.com/ajax/libs/moment.js/2.29.1/moment.min.js" integrity="sha512-qTXRIMyZIFb8iQcfjXWCO8+M5Tbc38Qi5WzdPOYZHIlZpzBHG3L3by84BBBOiRGiEb7KKtAOAs5qYdUiZiQNNQ==" crossorigin="anonymous" referrerpolicy="no-referrer"></script>

You need to create the svg element with svg namespace uri for it to support path when creating directly with JavaScript:
var svg = document.createElementNS('http://www.w3.org/2000/svg','svg');
Instead of just the typical
var svg = document.createElement('svg');
Alternatively, you could use D3 to append the svg, which will make sure it's correctly namespaced!
d3.select(child).append('svg').attr('id', 'donut');

d3 how to tie text to top right corner of view port while zooming and panning

I am creating a mapping application in d3 and want to tie some text to the top right corner of my view port. Additionally, I want the text to remain in the top right corner while I zoom and pan across the application.I think I can solve my problem by figuring out how to get the coordinates of the top right corner of my view. Knowing this information would allow me to then set the coordinates of my text element. I've tried manually setting the dimensions of the containing svg element and then moving the text to that location but interestingly this didn't work. I was hoping to be able to find the coordinates programatically rather than setting coordinates manually. How can I do this in d3/javascript?
EDIT:
My code is a modification of this code by Andy Barefoot: https://codepen.io/nb123456/pen/zLdqvM
My own zooming and panning code has essentially remained the same as the above example:
function zoomed() {
t = d3
.event
.transform
;
countriesGroup
.attr("transform","translate(" + [t.x, t.y] + ")scale(" + t.k + ")")
;
}
I'm trying to append the text at the very bottom of the code:
countriesGroup.append("text")
.attr("transform", "translate(" How do I get top right coordinates? ")")
.style("fill", "#ff0000")
.attr("font-size", "50px")
.text("This is a test");
My idea is to be able to get the top right coordinates of the view port through the code rather than setting it manually and then have the coordinates of the text update as the user zooms or pans.

To keep something in place while zooming and panning you could invert the zoom:
point == invertZoom(applyZoom(point))
This isn't particularly efficient, as we are using two operations to get to the original number. The zoom is applied here:
countriesGroup
.attr("transform","translate(" + [t.x, t.y] + ")scale(" + t.k + ")");
While the inversion would need to look something like:
text.attr("x", d3.zoom.transform.invert(point)[0])
.attr("y", d3.zoom.transform.invert(point)[1])
.attr("font-size", baseFontSize / d3.zoom.transform.k);
Where point and base font size are the original anchor point and font size. This means storing that data somewhere. In the example below I assign it as a datum to the text element:
var width = 500;
var height = 200;
var data = d3.range(100).map(function() {
return {x:Math.random()*width,y:Math.random()*height}
})
var zoom = d3.zoom()
.on("zoom",zoomed);
var svg = d3.select("body")
.append("svg")
.attr("width",width)
.attr("height",height)
.call(zoom);
var g = svg.append("g")
var circles = g.selectAll()
.data(data)
.enter()
.append("circle")
.attr("cx", function(d) { return d.x; })
.attr("cy", function(d) { return d.y; })
.attr("r", 5)
.attr("fill","steelblue")
var text = g.append("text")
.datum({x: width-10, y: 20, fontSize: 12})
.attr("x", function(d) { return d.x; })
.attr("y", function(d) { return d.y; })
.style("text-anchor","end")
.attr("font-size",function(d) { return d.fontSize; })
.text("This is a test");
function zoomed() {
g.attr("transform", d3.event.transform);
var d = text.datum();
var p = d3.event.transform.invert([d.x,d.y]);
var x1 = p[0];
var y1 = p[1];
text.attr("x",x1)
.attr("y",y1)
.attr("font-size", d.fontSize / d3.event.transform.k)
}
<script src="https://cdnjs.cloudflare.com/ajax/libs/d3/4.10.0/d3.min.js"></script>
Better Solution
The above is the solution to the approach you seem to be looking for. But the end result is best achieved by a different method. As I mention in my comment, the above approach goes through extra steps that can be avoided. There can also be some size/clarity changes in the text when zooming (quickly) using the above method
As noted above, you are applying the zoom here:
countriesGroup
.attr("transform","translate(" + [t.x, t.y] + ")scale(" + t.k + ")")
The zoom transform is applied only to countriesGroup, if your label happens to be in a different g (and not a child of countriesGroup), it won't be scaled or panned.
We wouldn't need to apply and invert the zoom, and we wouldn't need to update the position or font size of the text at all.
var width = 500;
var height = 200;
var data = d3.range(100).map(function() {
return {x:Math.random()*width,y:Math.random()*height}
})
var zoom = d3.zoom()
.on("zoom",zoomed);
var svg = d3.select("body")
.append("svg")
.attr("width",width)
.attr("height",height)
.call(zoom);
var g = svg.append("g");
var g2 = svg.append("g"); // order does matter in layering
var circles = g.selectAll()
.data(data)
.enter()
.append("circle")
.attr("cx", function(d) { return d.x; })
.attr("cy", function(d) { return d.y; })
.attr("r", 5)
.attr("fill","steelblue")
// position once and leave it alone:
var text = g2.append("text")
.attr("x", width - 10)
.attr("y", 20 )
.style("text-anchor","end")
.attr("font-size", 12)
.text("This is a test");
function zoomed() {
// apply the zoom to the g that has zoomable content:
g.attr("transform", d3.event.transform);
}
<script src="https://cdnjs.cloudflare.com/ajax/libs/d3/4.10.0/d3.min.js"></script>

User input to Project on JSON map

I have the following D3.js project that is available here:
http://bl.ocks.org/diggetybo/raw/e75dcb649ae3b26e2312a63434fc970c/
The latitude and longitude inputs are below the map.
It's supposed to take user input numbers of latitude and longitude and "project" svg circles at the given coordinate. The issue is I'm either getting ____ is not a function error or dev tools throws no errors at all, but the circles are never projected.
It's a short file, can someone explain why it's not working the way I thought?

Your update function doesn't make any sense.
It accepts two inputs, but you only ever call it with one.
.selectAll("circle").enter() is not valid d3 syntax.
You need to call projection with both the latitude and longitude, you pass 0 which will result in it returning null since it's outside of the projection.
After you fix all this, you'll still be off because you've moved your paths by your margin and would have been better off putting them in a g moved by the margins.
All that said, a simple rewrite would be:
var lat = d3.select("#latValue").on("input", function() {
update();
}).node();
var long = d3.select("#lonValue").on("input", function() {
update();
}).node();
function update() {
// lat/long to pixel
var coors = projection([long.value, lat.value]);
// if outside projection don't add circle
if (coors === null) return;
// add circle
container
.append("circle")
.attr("cx", coors[0])
.attr("cy", coors[1])
.attr("r", Math.sqrt(5) * 4)
.style("fill", "black")
.style("opacity", 0.85);
}
Running code:
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="utf-8">
<script src="http://d3js.org/d3.v3.min.js"></script>
<style type="text/css">
/* On mouse hover, lighten state color */
path:hover {
fill-opacity: .7;
}
</style>
</head>
<body>
<script type="text/javascript">
//Width and height of map
var width = 960;
var height = 500;
var margins = { left: 0, top: 100, right: 0, bottom: 0 };
// D3 Projection
var projection = d3.geo.albersUsa()
.translate([width/2, height/2]) // translate to center of screen
.scale([1000]); // scale things down so see entire US
// Define path generator
var path = d3.geo.path() // path generator that will convert GeoJSON to SVG paths
.projection(projection); // tell path generator to use albersUsa projection
// Define linear scale for output
var color = d3.scale.linear()
.range(["#c3e2ff","#15198e"]);
//Create SVG element and append map to the SVG
var svg = d3.select("body")
.append("svg")
.attr("width", width)
.attr("height", height+margins.top);
svg.append('text')
.text('Coordinate Query')
.attr('font-size','24px')
.attr('transform', 'translate(' + 30 + ',' +70 + ')')
.attr('font-family','Calibri');
svg.append('text')
.text('Data as of 12/2016')
.attr('font-size','12px')
.attr('transform', 'translate(' + 35 + ',' +100 + ')')
.attr('font-family','Calibri');
// Load in my states data!
color.domain([0,100]); // setting the range of the input data
// Load GeoJSON data and merge with states data
d3.json("https://jsonblob.com/api/573228c3-d068-11e6-b16a-b501dc8d2b08", function(json) {
//var coordinates = d3.mouse(this);
// Bind the data to the SVG and create one path per GeoJSON feature
var container = svg.append("g")
.attr('transform', 'translate(' + margins.left + ',' + margins.top + ')');
container.selectAll("path")
.data(json.features)
.enter()
.append("path")
.attr("d", path)
.style("stroke", "#fff")
.style("stroke-linejoin","round")
.style("stroke-width", "1.5")
.style("fill", 'steelblue');
// Modified Legend Code from Mike Bostock: http://bl.ocks.org/mbostock/3888852
var lat = d3.select("#latValue").on("input", function() {
update();
}).node();
var long = d3.select("#lonValue").on("input", function() {
update();
}).node();
function update() {
// lat/long to pixel
var coors = projection([long.value, lat.value]);
// if outside projection don't add circle
if (coors === null) return;
// add circle
container
.append("circle")
.attr("cx", coors[0])
.attr("cy", coors[1])
.attr("r", Math.sqrt(5) * 4)
.style("fill", "black")
.style("opacity", 0.85);
}
});
</script>
<p>
<label for="latValue"
style="display: inline-block;width:240px;text-align:right;font-size:18px;font-family:Play">
Lattitude:<span id="latValue-value"></span>
</label>
<input type="number"min="-360"max="360"step="1"value="0" id="latValue">
<label for="lonValue"
style="display: inline-block;width:240px;text-align:right;font-size:18px;font-family:Play">
Longitude:<span id="lonValue-value"></span>
</label>
<input type="number"min="-360"max="360"step="1"value="0" id="lonValue">
</p>
</body>
</html>

Is it possible to start a D3JS pie chart with all values being 0?

I'm making a simple tool to display a set of values that are manipulated by the user. I want all the values to start at 0 and when the data is manipulated, to grow from there.
I have everything setup except that I get errors in the console when I start all my values at 0.
Is this possible?
Here's the code I have at the moment (which is working if the values are greater than 0):
var width = this.get('width');
var height = this.get('height');
var radius = Math.min(width, height) / 2;
var color = this.get('chartColors');
var data = this.get('chartData');
var arc = d3.svg.arc()
.outerRadius(radius)
.innerRadius(0);
var pie = d3.layout.pie()
.sort(null)
.value(function(d) { return d.count; });
var id = this.$().attr('id');
var svg = d3.select("#"+id)
.attr("width", width)
.attr("height", height)
.append("g")
.attr("transform", "translate(" + width / 2 + "," + height / 2 + ")");
var g = svg.selectAll("path")
.data(pie(data));
g.enter()
.append("path")
.attr("d", arc)
.each(function(d){ this._current = d; })
.style("fill", function(d, i) { return color[i]; })
.style("stroke", "white")
.style("stroke-width", 2);

The problem is a conceptual one -- if everything is 0, how are you going to draw a pie chart? You could however start with an empty data set and add new data as it becomes greater than zero. That leaves the problem of animating the growth of a pie chart segment from 0 to its desired size.
For this, you can animate the end angle of the pie chart segments starting at the start angle. The easiest way to do this is to copy the corresponding data object and tween the angle:
.each(function(d) {
this._current = JSON.parse(JSON.stringify(d));
this._current.endAngle = this._current.startAngle;
})
.transition().duration(dur).attrTween("d", arcTween);
Random example here.

D3 - Pie Chart & Force Directed Labels

I'm looking to create a pie chart with floating labels using D3. I'm new to D3 and I'm not even sure this is possible? Can you use the labels of one graph in another somehow? If you can, can you point me to an example?
Shorter Explanation:
I want labels from:
http://bl.ocks.org/1691430
...to be on a pie chart.
Here's the code I was running below:
Or in a JSBIN: http://jsbin.com/awilak/1/edit
If I understand his code correctly, this is the section that adds the labels. I don't understand what the labelForce.update does. From there, I don't care about transition, so that line isn't needed. Then the rest is just drawing the circles and adds a link / line? If someone could integrate that would be amazing but if you can help me understand what's going on and what I'm missing I'd be more than grateful.
// Now for the labels
// This is the only function call needed, the rest is just drawing the labels
anchors.call(labelForce.update)
labels = svg.selectAll(".labels")
.data(data, function(d,i) {return i;})
labels.exit()
.attr("class","exit")
.transition()
.delay(0)
.duration(500)
.style("opacity",0)
.remove();
// Draw the labelbox, caption and the link
newLabels = labels.enter().append("g").attr("class","labels")
newLabelBox = newLabels.append("g").attr("class","labelbox")
newLabelBox.append("circle").attr("r",11)
newLabelBox.append("text").attr("class","labeltext").attr("y",6)
newLabels.append("line").attr("class","link")
labelBox = svg.selectAll(".labels").selectAll(".labelbox")
links = svg.selectAll(".link")
labelBox.selectAll("text").text(function(d) { return d.num})
}
<!DOCTYPE html>
<html>
<head>
<meta http-equiv="Content-type" content="text/html; charset=utf-8">
<title>Testing Pie Chart</title>
<script type="text/javascript" src="http://mbostock.github.com/d3/d3.js?2.1.3"></script>
<script type="text/javascript" src="http://mbostock.github.com/d3/d3.geom.js?2.1.3"></script>
<script type="text/javascript" src="http://mbostock.github.com/d3/d3.layout.js?2.1.3"></script>
<style type="text/css">
.slice text {
font-size: 16pt;
font-family: Arial;
}
</style>
</head>
<body>
<button id="button"> Test </button>
<br>
<form id="controls">
<div>
<h2>Y axis</h2>
<ul id="y-axis">
<li><label><input checked="checked" type="radio" name="y-axis" value="Component">Component</label></li>
<li><label><input type="radio" name="y-axis" value="Browser">Browser</label></li>
<li><label><input type="radio" name="y-axis" value="Version">Version</label></li>
</ul>
</div>
</form>
<script type="text/javascript">
// return a list of types which are currently selected
function plottableTypes () {
var types = [].map.call (document.querySelectorAll ("#coaster-types input:checked"), function (checkbox) { return checkbox.value;} );
return types;
}
var w = 600, //width
h = 600, //height
r = 100,
r2 = 200, //radius
axis = getAxis (), //axes
color = d3.scale.category20c(); //builtin range of colors
data = [
{"Browser":"Internet Explorer ","Version":"8.0","Toatl":2000,"Component":"6077447412293130422"},
{"Browser":"Internet Explorer ","Version":"9.0 ","Toatl":1852,"Component":"6077447412293130422"},
{"Browser":"Internet Explorer ","Version":"6.0 ","Toatl":1754,"Component":"6077447412293130422"},
{"Browser":"Firefox ","Version":"16.0 ","Toatl":1020,"Component":"6077447412293130422"},
{"Browser":"Chrome ","Version":"23.0 ","Toatl":972,"Component":"6077447412293130422"},
{"Browser":"Internet Explorer ","Version":"7.0 ","Toatl":700,"Component":"6077447412293130422"},
{"Browser":"Mobile Safari ","Version":"6.0 ","Toatl":632,"Component":"6077447412293130422"},
{"Browser":"BOT ","Version":"BOT ","Toatl":356,"Component":"6077447412293130422"},
{"Browser":"Firefox ","Version":"8.0 ","Toatl":196,"Component":"6077447412293130422"},
{"Browser":"Mobile Safari ","Version":"5.1 ","Toatl":184,"Component":"6077447412293130422"}
];
var vis = d3.select("body")
.append("svg:svg") //create the SVG element inside the <body>
.data([data]) //associate our data with the document
.attr("width", w) //set the width and height of our visualization (these will be attributes of the <svg> tag
.attr("height", h)
.append("svg:g") //make a group to hold our pie chart
.attr("transform", "translate(" + r2 + "," + r2 + ")") //move the center of the pie chart from 0, 0 to radius, radius
var arc = d3.svg.arc() //this will create <path> elements for us using arc data
.outerRadius(r);
var pie = d3.layout.pie() //this will create arc data for us given a list of values
.value(function(d) { return d.Toatl; }); //we must tell it out to access the value of each element in our data array
var arcs = vis.selectAll("g.slice") //this selects all <g> elements with class slice (there aren't any yet)
.data(pie) //associate the generated pie data (an array of arcs, each having startAngle, endAngle and value properties)
.enter() //this will create <g> elements for every "extra" data element that should be associated with a selection. The result is creating a <g> for every object in the data array
.append("svg:g") //create a group to hold each slice (we will have a <path> and a <text> element associated with each slice)
.attr("class", "slice"); //allow us to style things in the slices (like text)
arcs.append("svg:path")
.attr("fill", function(d, i) { return color(i); } ) //set the color for each slice to be chosen from the color function defined above
.attr("d", arc); //this creates the actual SVG path using the associated data (pie) with the arc drawing function
arcs.append("svg:text") //add a label to each slice
.attr("transform", function(d) { //set the label's origin to the center of the arc
//we have to make sure to set these before calling arc.centroid
d.innerRadius = r2;
d.outerRadius = r;
return "translate(" + arc.centroid(d) + ")"; //this gives us a pair of coordinates like [50, 50]
})
.attr("text-anchor", "middle") //center the text on it's origin
.text(function(d, i) {
if(axis.yAxis == "Component"){
return data[i].Component;
}
return data[i].Browser; //get the label from our original data array
});
d3.select('#button').on('click', reColor);
var arcOver = d3.svg.arc()
.outerRadius(r + 30)
.innerRadius(0);
var arc = d3.svg.arc()
.outerRadius(r)
.innerRadius(0);
var arcs = vis.selectAll("g.slice")
.attr("class", "slice")
.on("mouseover", function(d) {
getAxis();
d3.select(this)
.select("path")
.transition()
.duration(500)
.attr("d", arcOver);
d3.select(this).select("text")
.text(function(d, i) {
if(axis.yAxis == "Component"){
return data[i].Component;
}
return data[i].Browser; //get the label from our original data array
});
})
.on("mouseout", function(d) {
getAxis();
d3.select(this)
.select("path")
.transition()
.duration(500)
.attr("d", arc);
d3.select(this)
.select("text")
.text(function(d, i) {
if(axis.yAxis == "Component"){
return data[i].Component;
}
return data[i].Browser; //get the label from our original data array
});
});
function reColor(){
var slices = d3.select('body').selectAll('path');
slices.transition()
.duration(2000)
.attr("fill", function(d, i) { return color(i+2); } );
slices.transition()
.delay(2000)
.duration(2000)
.attr("fill", function(d, i) { return color(i+10); } )
}
function makeData(){
}
// return an object containing the currently selected axis choices
function getAxis () {
var y = document.querySelector("#y-axis input:checked").value;
return {
yAxis: y,
};
}
function update() {
axis = getAxis()
arcs.selectAll("text") //add a label to each slice
.text(function(d, i) {
if(axis.yAxis == "Component"){
return data[i].Component;
}
return data[i].Browser; //get the label from our original data array
});
}
document.getElementById("controls").addEventListener ("click", update, false);
document.getElementById("controls").addEventListener ("keyup", update, false);
</script>
</body>
</html>

As others mentioned in the comments to your introduction-post it's possible to achieve a solution like you described it and it's possible using your code plus parts of the "moving-labels"-example. If I understand you correctly, you want to achieve non-overlapping labels using the force-layout, which is a pretty nice idea that I didn't stumble upon yet.
The code-part you pasted from the example just draws the labels and the lines as you already explained correctly. The next step is to rearrange the labels in a force-like layout around your pie chart.
The part that rearranges the labels (and links) in the example is the following:
function redrawLabels() {
labelBox
.attr("transform",function(d) { return "translate("+d.labelPos.x+" "+d.labelPos.y+")"})
links
.attr("x1",function(d) { return d.anchorPos.x})
.attr("y1",function(d) { return d.anchorPos.y})
.attr("x2",function(d) { return d.labelPos.x})
.attr("y2",function(d) { return d.labelPos.y})
}
// Initialize the label-forces
labelForce = d3.force_labels()
.linkDistance(0.0)
.gravity(0)
.nodes([]).links([])
.charge(-60)
.on("tick",redrawLabels)
The function is the one that changes the positions of the labels and lines. The force is calculated by D3 and started with the d3.force_labels().... As you can see, the function is assigned as an event-handler for the tick-event. In other words: After every step of calculating the force, D3 calls the 'drawer' for every label and updates the positions.
Unfortunately I'm not very familiar with the force_labels() method of D3, but I would assume it works pretty much like the regular force().
An anchor, in your case, is placed somewhere in each pie-piece for each label. The more centered within each pie-piece (NOT the pie itself), the better. Unfortunately you have to calculate this anchor-position somehow (sin and cos stuff) and set the line-ends to this fixed position within redrawLabels().
After you've done this you will see the first result. You may have to play around with gravity, linkDistance etc values of the force to achieve good results. (That's what the silders in the example do.)
See d3 docs for more info: https://github.com/mbostock/d3/wiki/Force-Layout
Then you will maybe stumble upon the problem that the labels are ordered around the pie without overlapping but in some strange order. You could solve this by initially placing the labels in correct order on a larger circle around your pie instead of positioning them randomly around the panel, which is the cause for the problem. This way you will experience way less jitter and misplacements.
The idea also is described in another blocks example: http://bl.ocks.org/mbostock/7881887
In this example, the nodes are initially placed on a virtual circle. The positioning is calculated by the following functions:
x: Math.cos(i / m * 2 * Math.PI) * 200 + width / 2 + Math.random(),
y: Math.sin(i / m * 2 * Math.PI) * 200 + height / 2 + Math.random()
They represent a circle with a radius of 200, place in the center of the drawing-panel. The circle is divided into m equally large pieces. i/m just calculates the 'piece-positions' where i ranges from 0 to m-1.
Hope I could help!

Yes, you can definitely combine force-labels with a pie chart! There is nothing particularly special about the pie chart labels you started with, they're just text elements that can be positioned like anything else using transform or x/y. It looks like you were initially positioning these labels according to the centroids of the arcs they were labelling, but you can just as easily use another criteria (like the output of a force layout).
D3's force layout calculates positions for things based on a set of constraints about what is fixed, what is movable, and which are connected to which. The labelForce.update method from Mike's bl.ocks example is being used to inform the force layout about how many objects need to be positioned, and where the fixed "anchor" points are. It then saves the computed positions for the labels into the diagram's data model, and they are used later on in the redrawLabels function.

You need to create two arcs. One for the pie chart drawing, and one which is large for the labels to sit on.
// first arc used for drawing the pie chart
var arc = d3.svg.arc()
.outerRadius(radius - 10)
.innerRadius(0);
// label attached to first arc
g.append("text")
.attr("transform", function(d) { return "translate(" + arc.centroid(d) + ")"; })
.attr("dy", ".35em")
.style("text-anchor", "middle")
.text(function(d) { return d.data.age; });
// second arc for labels
var arc2 = d3.svg.arc()
.outerRadius(radius + 20)
.innerRadius(radius + 20);
// label attached to second arc
g.append("text")
.attr("transform", function(d) { return "translate(" + arc2.centroid(d) + ")"; })
.attr("dy", ".35em")
.style("text-anchor", "middle")
.text(function(d) { return d.data.age; });