Legend for radius

[nobarany]

Is there a way to produce a legend for radius? Setting the legend=true like the following doesn't seem to do anything.

    r: {
      legend: true,
      label: 'label',
      range: [3, 6],
      domain: [1, 1000],
      type: 'linear',
    },

[mbostock]

Please upvote this feature request: #236 Thanks!

[nobarany]

thank you!