Question

I’m playing a bit with D3.js and I got most things working. But I want to place my svg shapes in a circle. So I will show the difference in data with color and text. I know how to draw circles and pie charts, but I want to basically have a circle of same size circles. And not have them overlap, the order is irrelevant. I don’t know where to start, to find out the x & y for each circle.

Answer 1

Here’s another approach to this, for shapes of arbitrary size, using D3’s tree layout: http://jsfiddle.net/nrabinowitz/5CfGG/

The tree layout (docs, example) will figure out the x,y placement of each item for you, based on a given radius and a function returning the separation between the centers of any two items. In this example, I used circles of varying sizes, so the separation between them is a function of their radii:

var tree = d3.layout.tree()
    .size([360, radius])
    .separation(function(a, b) {
        return radiusScale(a.size) + radiusScale(b.size);
    });

Using the D3 tree layout solves the first problem, laying out the items in a circle. The second problem, as @Markus notes, is how to calculate the right radius for the circle. I’ve taken a slightly rough approach here, for the sake of expediency: I estimate the circumference of the circle as the sum of the diameters of the various items, with a given padding in between, then calculate radius from the circumference:

var roughCircumference = d3.sum(data.map(radiusScale)) * 2 +
        padding * (data.length - 1),
    radius = roughCircumference / (Math.PI * 2);

The circumference here isn’t exact, and this will be less and less accurate the fewer items you have in the circle, but it’s close enough for this purpose.