[unlisted] Using a sqrt scale

<!DOCTYPE html>
<html>
  <head>
    <title>Encoding Data with Size</title>
    <script src="https://d3js.org/d3.v4.min.js"></script>
  	<style>
      .axis .tick line {
        stroke-width: 2px;
        stroke: #dddddd;
      }
      .axis .tick text {
      	font-size: 30px;
        fill: #8E8883;
      }
      .axis .domain {
        display: none;
      }
      .axis__label {
        text-anchor: middle;
        font-size: 50px;
        fill: #635F5D;
      }
    </style>
  </head>
  <body>
    <svg width="960" height="500"></svg>
    <script>
      const xValue = d => d.sepalLength;
      const yValue = d => d.petalLength;
      const sizeValue = d => d.petalWidth;
      const sizeMax = 10;
      const xLabel = "Sepal Length";
      const yLabel = "Petal Length";
      const margin = {top: 30, right: 30, bottom: 100, left: 100};
      
      const svg = d3.select("svg");
      const width = +svg.attr("width");
      const height = +svg.attr("height");
      const innerWidth = width - margin.left - margin.right;
      const innerHeight = height - margin.top - margin.bottom;
      const xScale = d3.scaleLinear().range([0, innerWidth]);
      const yScale = d3.scaleLinear().range([innerHeight, 0]);
      const sizeScale = d3.scaleSqrt()
        .range([0, sizeMax]);
      
      const xAxis = d3.axisBottom()
        .scale(xScale)
        .tickSizeInner(-innerHeight)
        .tickPadding(15);
      const yAxis = d3.axisLeft()
        .scale(yScale)
        .tickSizeInner(-innerWidth)
        .ticks(5)
        .tickPadding(10);
      
      const g = svg.append("g")
          .attr("transform", `translate(${margin.left}, ${margin.top})`);
      const xAxisG = g.append("g")
          .attr("class", "axis")
          .attr("transform", `translate(0, ${innerHeight})`);
      const yAxisG = g.append("g")
          .attr("class", "axis");
      
      xAxisG
        .append("text")
          .attr("class", "axis__label")
          .attr("x", innerWidth / 2)
          .attr("y", 85)
          .text(xLabel);
      
      yAxisG
        .append("text")
          .attr("class", "axis__label")
          .attr("transform", "rotate(-90)")
          .attr("x", -innerHeight / 2)
          .attr("y", -45)
          .text(yLabel);
      
      function render(data){
        xScale
          .domain(d3.extent(data, xValue))
          .nice();
        yScale
          .domain(d3.extent(data, yValue))
          .nice();
        sizeScale
          .domain([0, d3.max(data, sizeValue)]);
        
        xAxisG.call(xAxis);
        yAxisG.call(yAxis);
        
        const circles = g.selectAll("circle").data(data);
        circles.exit().remove();
        circles
          .enter().append("circle")
            .attr("r", 5)
          .merge(circles)
            .attr("cx", d => xScale(xValue(d)))
            .attr("cy", d => yScale(yValue(d)))
            .attr("r", d => sizeScale(sizeValue(d)));
      }
            
      function type(d){
        d.sepalLength = +d.sepalLength;
        d.sepalWidth = +d.sepalWidth;
        d.petalLength = +d.petalLength;
        d.petalWidth = +d.petalWidth;
        return d;
      }
      
      d3.csv("iris.csv", type, render);
      
    </script>
  </body>
</html>

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