mere circles

<!DOCTYPE html>
<head>
  <meta charset="utf-8">
  <script src="https://d3js.org/d3.v4.min.js"></script>
  <style>
    body { margin:0;position:fixed;top:0;right:0;bottom:0;left:0; }
    svg {
      border: 1px solid blue;
    }
  </style>
</head>

<body>
  <script>
    const svg = d3.select('body')
    	.append('svg')
    	.attr('width', 650)
    	.attr('height', 450);

let data = generateData(30);

const scaleX = d3.scaleLinear()
    	.domain([0, 10])
    	.range([50, 550]);

const scaleY = d3.scaleLinear()
    	.domain([0, 10])
    	.range([50, 350]);

const scaleR = d3.scaleLinear()
    	.domain([0, 10])
    	.range([10, 100]);
 
    const scaleC = d3.scaleLinear()
    	.domain([0, 10])
    	.range([0, 1]);

//const colors = d3.scaleOrdinal(d3.schemeCategory20c);
    const rainbow = d3.scaleSequential(d3.interpolateRainbow);

svg.selectAll('circle')
    	.data(data)
    	.enter().append('circle')
    	.attr('cx', d => scaleX(d.x))
    	.attr('cy', d => scaleY(d.y))
    	.attr('r', d => scaleR(d.r))
    	.attr('fill', 'none')
    	.attr('stroke-width', 2)
    	.attr('stroke', d => {
      	// colors(d.r);
        return rainbow(scaleC(d.r));
    	});

// for fun let's modify the data
    const update = () => {
      const delta = 10;
      data = data
        .slice(delta)
      	.concat(generateData(delta));

const circles = svg.selectAll('circle')
      	.data(data, d => d.radius);
      
      circles.exit()
      	.attr('opacity', 1)
      	.transition()
      	.attr('r', d => scaleR(d.r) * 2)
      	.attr('opacity', 0)
	      .remove();

circles.enter().append('circle')
      	.attr('r', 0)
      	.attr('cx', d => scaleX(d.x))
      	.attr('cy', d => scaleY(d.y))
        .attr('fill', 'none')
        .attr('stroke-width', 2)
      	.attr('stroke', d => rainbow(scaleC(d.r)))
      	.attr('opacity', 0.3)
      .transition()
      	.duration(450)
    		.ease(d3.easeLinear)
      	.attr('opacity', 1)
      	.attr('r', d => scaleR(d.r));
    };
    setInterval(update, 1000);
  </script>
</body>

https://d3js.org/d3.v4.min.js