svg-sizing.js

// This can be generalized to arbitrary
// aspect ratios. See last example for
// more on that.

// See calculation for total size in
// example above
var size = 202; 

// 1st example - set an explicit
// width and height
d3.select('#example-1')
    .append('svg')
        .attr('width', size)
        .attr('height', size);
        
// 2nd example - viewbox
d3.select('#example-2')
    .append('svg')
        .attr('width', '100%')
        .attr('viewBox', '0 0 ' + size + ' ' + size);

// Note: all subsequent code inside of the
//       viewbox SVG can still assume a width
//       and height of 202, and it will automatically
//       scale correctly